Channel information sending method, data sending method, and device

ABSTRACT

A channel information sending method, a data sending method, and a device are provided, to improve feedback precision of a precoding matrix. These include a receiver that receives a reference signal and a memory, configured to store at least one computer instruction which, when executed by the processor, cause the processor to measure the reference signal from the receiver to obtain first channel information and second channel information and send the first channel information and the second channel information to the second device. In some embodiments, the first channel information comprises identification information of N antenna ports in M antenna ports for the reference signal, M is an integer not less than 2, and N is a positive integer not greater than M, the second channel information comprises information about a weighted combination factor used for performing weighted combination on the N antenna ports, the weighted combination factor comprises an amplitude factor and a phase factor, and the first channel information and the second channel information are used to constitute a precoding matrix.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/188,911, filed on Nov. 13, 2018, which is a continuation ofInternational Application No. PCT/CN2017/083978, filed on May 11, 2017.The International Application claims priority to Chinese PatentApplication No. 201610319166.9, filed on May 13, 2016. All of theafore-mentioned patent applications are hereby incorporated by referencein their entireties as if reproduced in full.

TECHNICAL FIELD

The present invention relates to the field of wireless communicationstechnologies, and in particular, to a channel information sendingmethod, a data sending method, and a device.

BACKGROUND

Currently, in a Long Term Evolution (LTE) frequency division duplex(FDD) system, user equipment (UE) performs channel estimation based on areference signal sent by a base station, then determines channel stateinformation, and feeds back the channel state information. The channelstate information includes a rank indicator (RI), a precoding matrixindex (PMI), and a channel quality indicator (CQI).

The PMI is an index of a precoding matrix. The UE feeds back the PMI tothe base station, and the base station determines the correspondingprecoding matrix based on the received PMI, and performs precodingprocessing based on the determined precoding matrix, to improve downlinkcommunication quality.

Currently, a manner of feeding back the PMI in the LTE FDD system isfeeding back a precoding matrix W based on a dual-stage codebookstructure:

W=W ₁ ×W ₂  Formula 1

where

$W_{1} = {\begin{bmatrix}b_{0} & b_{1} & \ldots & b_{M} & 0 & 0 & \ldots & 0 \\0 & 0 & \ldots & 0 & b_{0} & b_{1} & \ldots & b_{M - 1}\end{bmatrix}.}$

Herein, b₀, b₁, . . . , b_(M-1) are vectors included in a code word W₁corresponding to the precoding matrix W, and may be DFT vectors, where Mis an integer not less than 2. A vector b, is a column vector whoselength is a quantity of transmit antenna ports of the base station. Avalue ofM may be a preset value or may be a value preconfigured by thebase station.

When a channel matrix rank is equal to 1, there is:

$\begin{matrix}{W_{2} = \begin{bmatrix}e_{k} \\{\varphi_{n}e_{k}}\end{bmatrix}} & {{Formula}\mspace{14mu} 2}\end{matrix}$

When a channel matrix rank is equal to 2, there is:

$\begin{matrix}{W_{2} = \begin{bmatrix}e_{k} & e_{i} \\{\phi_{n}e_{k}} & {{- \phi_{n}}e_{i}}\end{bmatrix}} & {{Formula}\mspace{14mu} 3}\end{matrix}$

Herein, W₁ indicates a set including M vectors, and W₂ includes columnselection information and co-phase information.

Column selection information e_(k) is an M×1 unit vector, only a valueof a k^(th) element is 1, and values of all other elements are 0. A caseof e_(i) is similar to that of e_(k).

Co-phase information φ_(n) is a phase difference between twopolarization directions of transmit antennas of a second device 102, anda value is any number in a range from 0 to 2π.

In the current dual-stage codebook structure, W₂ can only be used toselect one vector from the M vectors: b₀, b₁, . . . , and b_(M-1).Consequently, feedback of the precoding matrix W is not sufficientlyprecise.

SUMMARY

In view of this, a channel information sending method, a data sendingmethod, and a device are provided, to improve feedback precision ofchannel information related to a precoding matrix, and further improvedownlink adaptation performance.

According to a first aspect, an embodiment of the present inventionprovides a channel information sending method, including:

sending, by a second device, a reference signal to a first device, wherethe reference signal is sent on S antenna ports, the S antenna portsbelong to H reference signal resource port groups, and H is an integergreater than or equal to 1; after receiving the reference signal,measuring, by the first device, the received reference signal, andobtaining and sending first channel information and second channelinformation to the second device; and generating, by the second device,a precoding matrix based on the received first channel information andthe received second channel information, and sending data to the firstdevice based on the generated precoding matrix.

The first channel information includes identification information of Mfirst vectors, where M is an integer not less than 2. The second channelinformation includes information about a weighted combination factorused for performing weighted combination on N first vectors in the Mfirst vectors, where N is a positive integer not greater than M. Theweighted combination factor includes a first factor and/or a secondfactor. The first factor is an amplitude factor, and the second factoris a phase factor or a time delay factor.

A dimension of the first vector is a quantity of antenna ports in eachreference signal resource port group, or a dimension of the first vectoris half of a quantity of antenna ports in each reference signal resourceport group.

The first device performs channel estimation based on the receivedreference signal, and feeds back, to the second device, the secondchannel information of the weighted combination factor used forperforming weighted combination on the M first vectors. In this way,when generating the precoding matrix, the second device may performweighted combination on the M first vectors based on the weightedcombination factor indicated by the received second channel information,instead of selecting only one eigenvector from a plurality ofeigenvectors, so that the generated precoding matrix is more precise,thereby improving a link adaptation capability of the second device forsending data, and improving system performance.

Optionally, the weighted combination factor includes an element 0, sothat the N first vectors are selected.

Optionally, the first device further measures the reference signal toobtain third channel information, and sends the third channelinformation to the second device.

The third channel information is used to indicate a phase differencebetween two groups of antenna ports for the reference signal, and thesecond device generates the precoding matrix based on the first channelinformation, the second channel information, and the third channelinformation.

Optionally, the first device further measures the reference signal toobtain fourth channel information, and sends the fourth channelinformation to the second device.

The fourth channel information includes selection information used toselect the N first vectors from the M first vectors.

The second device generates the precoding matrix based on the firstchannel information, the second channel information, and the fourthchannel information. Optionally, the second device may generate theprecoding matrix based on the third channel information. The secondchannel information includes only the information about the weightedcombination factor used for performing weighted combination on the Nfirst vectors indicated by the fourth channel information.

The first device feeds back the fourth channel information, so that theN first vectors can be selected, and accordingly an information feedbackamount of the second channel information is reduced.

Optionally, the first device further measures the reference signal toobtain seventh channel information, and sends the seventh channelinformation to the second device. The seventh channel informationincludes identification information used to select Y reference signalresource port groups from the H reference signal resource port groups.The second device generates the precoding matrix based on the firstchannel information, the second channel information, and the seventhchannel information. Optionally, the second device may generate theprecoding matrix based on the third channel information and/or thefourth channel information.

Optionally, the seventh channel information is not fed back in a samesubframe as other channel information.

Optionally, the first channel information includes a group number, in Kvector groups, of each of X vector groups including the M first vectors,and all first vectors in the K vector groups constitute a universal setof the first vectors, where K is a positive integer, and X is a positiveinteger not greater than K.

Optionally, the M first vectors are obtained by performing measurementbased on the Y reference signal resource port groups selected from the Hreference signal resource port groups, where Y is a positive integer.

Optionally, the M first vectors correspond to the X vector groups, eachvector group corresponds to one of the Y reference signal resource portgroups, and X=Y. Alternatively, the M first vectors correspond to the Xvector groups, at least two vector groups correspond to one of the Yreference signal resource port groups, and X>Y.

The M first vectors are grouped, so that a plurality of strong beamgroups may be selected, the generated precoding matrix can better adaptto an actual channel condition, and link adaptation performance isimproved.

Optionally, the first device sends, to the second device, informationused to indicate a value of X. Alternatively, the first device receives,from the second device, information used to indicate a value of X.

Optionally, different vector groups in the K vector groups include or donot include a same first vector.

Different vector groups in the K vector groups include a same quantityof first vectors or different quantities of first vectors.

Optionally, different vector groups in the X vector groups correspond tothe same second channel information, and for the different vectorgroups, the first device feeds back only one same piece of secondchannel information; or

different vector groups correspond to different second channelinformation, and for the different vector groups, the first deviceseparately feeds back the second channel information.

Optionally, each piece of channel information may be fed back in aflexible feedback manner, to improve channel information feedbackprecision, and reduce an information feedback amount as much aspossible.

For example, a feedback manner of the first channel information iswideband based feedback, and a feedback manner of the second channelinformation is subband based feedback. Alternatively, both a feedbackmanner of the first channel information and a feedback manner of thesecond channel information are subband based feedback, and feedbackbandwidth for the first channel information is greater than feedbackbandwidth for the second channel information.

A feedback period of the first channel information is longer than afeedback period of the second channel information.

For another example, a feedback manner of the first channel informationis wideband based feedback, and a feedback manner of the second channelinformation and a feedback manner of the third channel information aresubband based feedback. Alternatively, a feedback manner of the firstchannel information, a feedback manner of the second channelinformation, and a feedback manner of the third channel information areall subband based feedback, and feedback bandwidth for the first channelinformation is greater than feedback bandwidth for the second channelinformation and feedback bandwidth for the third channel information.

A feedback period of the first channel information is longer than afeedback period of the second channel information and a feedback periodof the third channel information.

For another example, a feedback manner of the first channel informationand a feedback manner of the second channel information are widebandbased feedback, and a feedback manner of the third channel informationis subband based feedback. Alternatively, both feedback bandwidth forthe first channel information and feedback bandwidth for the secondchannel information are greater than feedback bandwidth for the thirdchannel information.

A feedback manner of the first channel information and a feedback mannerof the second channel information are long-term feedback, and a feedbackmanner of the third channel information is short-term feedback.

Alternatively, both a feedback period of the first channel informationand a feedback period of the second channel information are longer thana feedback period of the third channel information.

For another example, a feedback manner of the first channel informationis wideband based feedback, and a feedback manner of the second channelinformation, a feedback manner of the third channel information, and afeedback manner of the fourth channel information are all subband basedfeedback. Alternatively, feedback bandwidth for the first channelinformation is greater than feedback bandwidth for the second channelinformation, feedback bandwidth for the third channel information, andfeedback bandwidth for the fourth channel information.

A feedback period of the first channel information is longer than afeedback period of the second channel information, a feedback period ofthe third channel information, and a feedback period of the fourthchannel information.

Optionally, both a feedback manner of the first channel information anda feedback manner of the second channel information are wideband basedfeedback, and both a feedback manner of the third channel informationand a feedback manner of the fourth channel information are subbandbased feedback. Alternatively, feedback bandwidth for the first channelinformation and feedback bandwidth for the second channel informationare greater than feedback bandwidth for the third channel informationand feedback bandwidth for the fourth channel information.

A feedback period of the first channel information and a feedback periodof the second channel information are longer than a feedback period ofthe third channel information and a feedback period of the fourthchannel information.

Optionally, a feedback manner of the first channel information, afeedback manner of the second channel information, and a feedback mannerof the fourth channel information are all wideband based feedback, and afeedback manner of the third channel information is subband basedfeedback. Alternatively, feedback bandwidth for the first channelinformation, feedback bandwidth for the second channel information, andfeedback bandwidth for the fourth channel information are greater thanfeedback bandwidth for the third channel information.

A feedback period of the first channel information, a feedback period ofthe second channel information, and a feedback period of the fourthchannel information are longer than a feedback period of the thirdchannel information.

Optionally, both a feedback manner of the first channel information anda feedback manner of the fourth channel information are wideband basedfeedback, and both a feedback manner of the second channel informationand a feedback manner of the third channel information are subband basedfeedback. Alternatively, feedback bandwidth for the first channelinformation and feedback bandwidth for the fourth channel informationare greater than feedback bandwidth for the second channel informationand feedback bandwidth for the third channel information.

A feedback period of the first channel information and a feedback periodof the fourth channel information are longer than a feedback period ofthe second channel information and a feedback period of the thirdchannel information.

Optionally, the first device measures the reference signal to obtainfifth channel information and sixth channel information, and the firstdevice sends the fifth channel information and the sixth channelinformation to the second device.

The fifth channel information includes information used to indicate anamount of spatially multiplexed data from the second device to the firstdevice, and the sixth channel information includes information used toindicate channel quality of a channel from the second device to thefirst device.

The second device further generates the precoding matrix based on thefifth channel information and the sixth channel information.

The first channel information and the fifth channel information are fedback in a first subframe by using a first period, and the second channelinformation and the sixth channel information are fed back in a secondsubframe by using a second period, where the first period is not lessthan the second period; or

the first channel information and the fifth channel information are fedback in a first subframe by using a first period, the second channelinformation is fed back in a second subframe by using a second period,and the sixth channel information is fed back in a third subframe byusing a third period, where the first period is not less than the secondperiod, and the second period is not less than the third period; or

the first channel information and the fifth channel information are fedback in a first subframe by using a first period, the second channelinformation is fed back in a second subframe by using a second period,and the sixth channel information is fed back in a third subframe byusing a third period, where the first period is not less than the secondperiod, and the second period is not less than the third period; or

the fifth channel information is fed back in a first subframe by using afirst period, the first channel information is fed back in a secondsubframe by using a second period, the second channel information is fedback in a third subframe by using a third period, and the sixth channelinformation is fed back in a fourth subframe by using a fourth period,where the first period is not less than the second period, the secondperiod is not less than the third period, and the third period is notless than the fourth period.

Alternatively, when the third channel information is fed back,

the first channel information and the fifth channel information are fedback in a first subframe by using a first period, the second channelinformation and the third channel information are fed back in a secondsubframe by using a second period, and the sixth channel information isfed back in a third subframe by using a third period, where the firstperiod is not less than the second period, and the second period is notless than the third period; or

the first channel information and the fifth channel information are fedback in a first subframe by using a first period, and the second channelinformation, the third channel information, and the sixth channelinformation are fed back in a second subframe by using a second period,where the first period is not less than the second period; or

the first channel information, the second channel information, and thefifth channel information are fed back in a first subframe by using afirst period, and the third channel information and the sixth channelinformation are fed back in a second subframe by using a second period,where the first period is not less than the second period; or

the first channel information and the fifth channel information are fedback in a first subframe by using a first period, the second channelinformation is fed back in a second subframe by using a second period,and the third channel information and the sixth channel information arefed back in a third subframe by using a third period, where the firstperiod is not less than the second period, and the second period is notless than the third period; or

the first channel information and the fifth channel information are fedback in a first subframe by using a first period, the second channelinformation is fed back in a second subframe by using a second period,the third channel information is fed back in a third subframe by using athird period, and the sixth channel information is fed back in a fourthsubframe by using a fourth period, where the first period is not lessthan the second period, the second period is not less than the thirdperiod, and the third period is not less than the fourth period; or

the fifth channel information is fed back in a first subframe by using afirst period, the first channel information is fed back in a secondsubframe by using a second period, the second channel information is fedback in a third subframe by using a third period, the third channelinformation is fed back in a fourth subframe by using a fourth period,and the sixth channel information is fed back in a fifth subframe byusing a fifth period, where the first period is not less than the secondperiod, the second period is not less than the third period, the thirdperiod is not less than the fourth period, and the fourth period is notless than the fifth period.

Alternatively, when the fourth channel information is fed back,

the first channel information, the fourth channel information, and thefifth channel information are fed back in a first subframe by using afirst period, the second channel information and the third channelinformation are fed back in a second subframe by using a second period,and the sixth channel information is fed back in a third subframe byusing a third period, where the first period is not less than the secondperiod, and the second period is not less than the third period; or

the first channel information, the fourth channel information, and thefifth channel information are fed back in a first subframe by using afirst period, and the second channel information, the third channelinformation, and the sixth channel information are fed back in a secondsubframe by using a second period, where the first period is not lessthan the second period; or

the fifth channel information is fed back in a first subframe by using afirst period, the first channel information and the fourth channelinformation are fed back in a second subframe by using a second period,the second channel information and the third channel information are fedback in a third subframe by using a third period, and the sixth channelinformation is fed back in a fourth subframe by using a fourth period,where the first period is not less than the second period, the secondperiod is not less than the third period, and the third period is notless than the fourth period; or

the fifth channel information is fed back in a first subframe by using afirst period, the first channel information and the fourth channelinformation are fed back in a second subframe by using a second period,and the second channel information, the third channel information, andthe sixth channel information are fed back in a third subframe by usinga third period, where the first period is not less than the secondperiod, and the second period is not less than the third period; or

the fifth channel information, the first channel information, the secondchannel information, and the fourth channel information are fed back ina first subframe by using a first period, and the third channelinformation and the sixth channel information are fed back in a secondsubframe by using a second period, where the first period is not lessthan the second period; or

the fifth channel information, the first channel information, and thefourth channel information are fed back in a first subframe by using afirst period, the second channel information is fed back in a secondsubframe by using a second period, and the third channel information andthe sixth channel information are fed back in a third subframe by usinga third period, where the first period is not less than the secondperiod, and the second period is not less than the third period; or

the fifth channel information, the first channel information, and thefourth channel information are fed back in a first subframe by using afirst period, the second channel information is fed back in a secondsubframe by using a second period, the third channel information is fedback in a third subframe by using a third period, and the sixth channelinformation is fed back in a fourth subframe by using a fourth period,where the first period is not less than the second period, the secondperiod is not less than the third period, and the third period is notless than the fourth period; or

the fifth channel information is fed back in a first subframe by using afirst period, the first channel information and the fourth channelinformation are fed back in a second subframe by using a second period,the second channel information is fed back in a third subframe by usinga third period, the third channel information is fed back in a fourthsubframe by using a fourth period, and the sixth channel information isfed back in a fifth subframe by using a fifth period, where the firstperiod is not less than the second period, the second period is not lessthan the third period, the third period is not less than the fourthperiod, and the fourth period is not less than the fifth period.

Optionally, the first channel information, the second channelinformation, and the third channel information constitute, in thefollowing manner, the precoding matrix whose rank is 1:

${W = {{\frac{1}{q}\begin{bmatrix}B_{i} & 0 \\0 & B_{i}\end{bmatrix}}\begin{bmatrix}c_{k} \\{\phi_{n}c_{k}}\end{bmatrix}}};{where}$ ${c_{k} = \begin{bmatrix}c_{k,0} & \ldots & c_{k,m} & \ldots & c_{k,{M - 1}}\end{bmatrix}^{T}},{B_{i} = \begin{bmatrix}b_{i,0} & \ldots & b_{i,m} & \ldots & b_{i,{M - 1}}\end{bmatrix}}$

B₁ is the M first vectors; c_(k) is the weighted combination factor,where c_(k,0) is used to perform weighting on b_(i,0), c_(k,m) is usedto perform weighting on b_(i,m), and c_(k,M-1) is used to performweighting on b_(i,M-1); m is an integer, and 0≤m≤M; Φ_(n) is the phasedifference that is between the two groups of antenna ports for thereference signal and that is indicated by the third channel information;and ∥q∥ is a normalization factor.

Optionally, B_(i) is a vector group whose group number is i in the Kvector groups.

All the first vectors in the K vector groups constitute the universalset of the first vectors, and K is a positive integer.

The first channel information includes information used to indicate i.

Optionally, B_(i)=[B_(i) ₀ . . . B_(i) _(x) . . . B_(i) _(X-1) ], wherethe X vector groups B_(i) ₀ . . . B_(i) _(x) . . . B_(i) _(X-1) arevector groups whose group numbers are sequentially i₀ to i_(X-1) in theK vector groups, x is an integer, 0≤x≤X−1, and X is a positive integer.

All the first vectors in the K vector groups constitute the universalset of the first vectors, and K is a positive integer.

The first channel information includes information separately used toindicate i₀ to i_(X-1).

Optionally, the first channel information, the second channelinformation, the third channel information, and the fourth channelinformation constitute, in the following manner, the precoding matrixwhose rank is 1:

${W = {{{\frac{1}{q}\begin{bmatrix}B_{i} & 0 \\0 & B_{i}\end{bmatrix}}\begin{bmatrix}e_{m_{0}} & \ldots & e_{m_{N - 1}} & 0 & 0 & 0 \\0 & 0 & 0 & e_{m_{0}} & \ldots & e_{m_{N - 1}}\end{bmatrix}}\begin{bmatrix}c_{k} \\{\phi_{n}c_{k}}\end{bmatrix}}};$ where ${c_{k} = \begin{bmatrix}c_{k,0} & \ldots & c_{k,m} & \ldots & c_{k,{N - 1}}\end{bmatrix}^{T}},{{{{and}\mspace{14mu} B_{i}} = \begin{bmatrix}b_{i,0} & b_{i,m} & \ldots & b_{i,{M - 1}}\end{bmatrix}};}$

B_(i) is the M first vectors; c_(k) is the weighted combination factorused for performing weighted combination on the N first vectors, wherec_(k,0) is used to perform weighting on b_(i,m) ₀ , c_(k,m) is used toperform weighting on b_(i,m) _(m) , and c_(k,N-1) is used to performweighting on b_(i,m) _(N-1) ; m is an integer, and 0≤m≤M−1; φ_(n) is thephase difference that is between the two groups of antenna ports for thereference signal and that is indicated by the third channel information;a quantity of rows of e_(m) ₀ ˜e_(m) _(N-1) is M, and the fourth channelinformation is information used to indicate m₀ to m_(N-1), and ∥q∥ is anormalization factor.

Optionally, the first device sends, to the second device, informationused to indicate a value of N. Alternatively, the first device receives,from the second device, information used to indicate a value of N.

Optionally, the fourth channel information is used to indicate

$\begin{bmatrix}e_{m_{0}} & \ldots & e_{m_{N - 1}} & 0 & 0 & 0 \\0 & 0 & 0 & e_{m_{0}} & \ldots & e_{m_{N - 1}}\end{bmatrix}.$

Alternatively, the fourth channel information includes M bits. In the Mbits, an m₀ ^(th) bit to an m_(N-1) ^(th) bit are 1, and remaining bitsare 0.

Optionally, the first channel information, the second channelinformation, and the third channel information constitute, in thefollowing manner, the precoding matrix whose rank is 2:

${W = {\frac{1}{q}\begin{bmatrix}{B_{i} \cdot c_{k}} & {B_{j} \cdot c_{y}} \\{\phi_{n}{B_{i} \cdot c_{k}}} & {{- \phi_{n}}{B_{j} \cdot c_{y}}}\end{bmatrix}}};{where}$ ${c_{k} = \begin{bmatrix}c_{k,0} & c_{k,m} & \ldots & c_{k,{R - 1}}\end{bmatrix}^{T}},{{B_{i} = \begin{bmatrix}b_{i,0} & b_{i,m} & \ldots & b_{i,{R - 1}}\end{bmatrix}};}$ ${c_{y} = \begin{bmatrix}c_{y,0} & c_{y,n} & \ldots & c_{y,{S - 1}}\end{bmatrix}^{T}},{{B_{j} = \begin{bmatrix}b_{j,0} & b_{j,n} & \ldots & b_{j,{S - 1}}\end{bmatrix}};}$

R and S are positive integers, R≤M, S≤M, and B_(i) and B_(j) jointlyconstitute the M first vectors; and

c_(k) and c_(y) are weighted combination factors, where c_(k,0) is usedto perform weighting on b_(i,0), c_(k,m) is used to perform weighting onb_(i,m), c_(k,R-1) is used to perform weighting on b_(i,R-1), c_(y,0) isused to perform weighting on b_(j,0), c_(y,n) is used to performweighting on b_(j,n), and c_(y,S-1), is used to perform weighting onb_(j,S-1); m is an integer, and 0≤m≤R−1; n is an integer, and 0≤n≤S−1;φ_(n) is the phase difference that is between the two groups of antennaports for the reference signal and that is indicated by the thirdchannel information; and ∥q∥ is a normalization factor.

Optionally, B_(i) is the same as B_(j), and c_(k) is different fromc_(m); or

B_(i) is different from B_(j), and c_(k) is the same as c_(m); or

B_(i) is different from B_(j), and c_(k) is different from c_(m); or

B_(i) is the same as B_(j), and c_(k) is the same as c_(m).

Optionally, B_(i)=[B_(i) ₀ . . . B_(i) _(x) . . . B_(i) _(X-1) ].

The X vector groups B_(i) ₀ . . . B_(i) _(x) . . . B_(i) _(X-1) arevector groups whose group numbers are sequentially i₀ to i_(X-1) in theK vector groups, x is an integer, 0≤x≤X−1, and X is a positive integer.

All the first vectors in the K vector groups constitute the universalset of the first vectors, and K is a positive integer.

The first channel information includes information separately used toindicate i₀ to i_(X-1).

B_(i) ₀ corresponds to a first reference signal resource port group inthe Y reference signal resource port groups in an H reference signalresource port group, B_(i) _(x) corresponds to an x^(th) referencesignal resource port group in the Y reference signal resource portgroups in the H reference signal resource port group, and B_(i) _(x)corresponds to an X^(th) reference signal resource port group in the Yreference signal resource port groups in the H reference signal resourceport group.

Optionally, the second channel information is a time delay factor.

A form that is of the precoding matrix including the first channelinformation and the second channel information and that is in timedomain is as follows:

${{W(\tau)} = {\sum\limits_{m = 0}^{N - 1}{b_{i,m}p_{m}{\delta \left( {\tau - \tau_{m}} \right)}}}};$

τ_(m) is the time delay factor corresponding to an m^(th) vector in theN first vectors.

Optionally, B_(i) is the M first vectors, and B_(i)=[b_(i,0) b_(i,m) . .. b_(i,M-1)].

Each first vector in B_(i) is a Kronecker product of a second vector ina second vector group and a third vector in a third vector group:b_(i,m)=a_(p,m) ₁ ⊗d_(t,m) ₂ , where

b_(i,m) is the first vector, a_(p,m) ₁ is the second vector whose numberis m₁ in the second vector group whose number is p, and d_(t,m) ₂ is thethird vector whose number is m₂ in the third vector group whose numberis t.

The first channel information includes first subchannel information andsecond subchannel information.

The first subchannel information is used to indicate p, and the secondsubchannel information is used to indicate t.

${a_{p,m_{1}} = \begin{bmatrix}1 & e^{j\; 2\; \pi \frac{({{p*S_{1}} + m_{1}})}{N_{1}Q_{1}}} & \ldots & e^{j\; 2\; \pi \frac{{{({N_{1} - 1})})}{({{p*S_{1}} + m_{1}})}}{N_{1}Q_{1}}}\end{bmatrix}^{T}},$

where N₁ is a quantity of first-dimension antenna ports in an antennaarray, Q₁ is a factor used for oversampling DFT vectors that constitutea code word set of first-dimension antennas, and s₁ is a positiveinteger.

${d_{t,m_{2}} = \begin{bmatrix}1 & e^{j\; 2\; \pi \frac{({{p*S_{2}} + m_{2}})}{N_{2}Q_{2}}} & \ldots & e^{j\; 2\; \pi \frac{{{({N_{1} - 1})})}{({{t*S_{2}} + m_{2}})}}{N_{2}Q_{2}}}\end{bmatrix}^{T}},$

where N₂ is a quantity of second-dimension antenna ports in the antennaarray, Q₂ is a factor used for oversampling DFT vectors that constitutea code word set of second-dimension antennas, and S₂ is a positiveinteger.

Optionally, a quantity of second vector groups is greater than or equalto 2, and a quantity of third vector groups is equal to 1; or

a quantity of third vector groups is greater than or equal to 2, and aquantity of second vector groups is equal to 1; or

a quantity of third vector groups is equal to 1, and a quantity ofsecond vector groups is equal to 1.

Optionally, the second vector and the third vector are DFT vectors.

A quantity of vectors included in a universal set of second vectors anda quantity of vectors included in a universal set of third vectors aremutually independently configured.

Optionally, the second channel information includes third subchannelinformation, and the third subchannel information is used to indicatethe first factor.

The third subchannel information is not quantized.

Alternatively, first quantization is performed on the third subchannelinformation, and a quantization order of the first quantization is notgreater than a preset first-quantization order threshold.

Optionally, the second channel information includes fourth subchannelinformation, and the fourth subchannel information is used to indicatethe second factor.

The fourth subchannel information is not quantized.

Alternatively, second quantization is performed on the fourth subchannelinformation, and a quantization order of the second quantization is notless than a preset second-quantization order threshold.

According to a second aspect, an embodiment of the present inventionprovides a first device, and the first device has a function ofimplementing behavior of the first device in the foregoing method. Thefunction may be implemented by using hardware, or may be implemented byexecuting corresponding software by hardware. The hardware or thesoftware includes one or more modules corresponding to the function.

In an optional implementation solution, a structure of the first deviceincludes a processor, a transmitter, and a receiver. The processor isconfigured to support the first device in performing the correspondingfunction in the foregoing method. The transmitter is configured tosupport the first device in sending a message or data in the foregoingmethod to a second device. The receiver is configured to receive themessage or the data in the foregoing method from the second device. Thefirst device may further include a memory, and the memory is configuredto couple to the processor, and stores a program instruction and datathat are necessary for the first device.

According to a third aspect, an embodiment of the present inventionprovides a second device, and the second device has a function ofimplementing behavior of the second device in the foregoing method. Thefunction may be implemented by using hardware, or may be implemented byexecuting corresponding software by hardware. The hardware or thesoftware includes one or more modules corresponding to the function.

In an optional implementation solution, a structure of the second deviceincludes a transmitter, a receiver, and a processor. The receiver isconfigured to support the second device in receiving a message or datain the foregoing method from a first device. The transmitter isconfigured to support the second device in sending the message or thedata in the foregoing method to the first device. The processor isconfigured to support the second device in performing the correspondingfunction in the foregoing method. The second device may further includea memory, and the memory is configured to couple to the processor, andstores a program instruction and data that are necessary for the seconddevice.

According to a fourth aspect, an embodiment of the present inventionprovides a wireless communications system, and the wirelesscommunications system includes the first device and the second deviceaccording to any one of the first aspect to the third aspect.

According to a fifth aspect, an embodiment of the present inventionprovides a computer storage medium. The computer storage medium isconfigured to store a computer software instruction used by the firstdevice according to any one of the first aspect to the fourth aspect,and includes a program designed for executing the foregoing aspects.

According to a sixth aspect, an embodiment of the present inventionprovides a computer storage medium. The computer storage medium isconfigured to store a computer software instruction used by the seconddevice according to any one of the first aspect to the fourth aspect,and includes a program designed for executing the foregoing aspects.

According to a seventh aspect, an embodiment of the present inventionprovides a channel information sending method, including:

sending, by a second device, a reference signal to a first device;receiving, by the first device, the reference signal sent by the seconddevice; after receiving the reference signal, measuring, by the firstdevice, the received reference signal, to obtain first channelinformation and second channel information, and sending the firstchannel information and the second channel information to the seconddevice; and generating, by the second device, a precoding matrix basedon the received first channel information and the received secondchannel information, and sending data to the first device based on thegenerated precoding matrix.

The first channel information includes identification information of Nantenna ports in M antenna ports for the reference signal, where M is aninteger not less than 2, and N is a positive integer not greater than M.The second channel information includes information about a weightedcombination factor used for performing weighted combination on the Nantenna ports. The weighted combination factor includes a first factorand/or a second factor. The first factor is an amplitude factor, and thesecond factor is a phase factor or a time delay factor.

The first device performs channel estimation based on the receivedreference signal, and feeds back, to the second device, the secondchannel information of the weighted combination factor used forperforming weighted combination on the M antenna ports for the referencesignal. In this way, when generating the precoding matrix, the seconddevice may perform weighted combination on the M antenna ports based onthe weighted combination factor indicated by the received second channelinformation, so that a relatively precise precoding matrix can also begenerated, thereby also improving a link adaptation capability of thesecond device for sending data, and improving system performance.

Optionally, the weighted combination factor includes an element 0, sothat the N antenna ports are selected.

Optionally, the first device measures the reference signal to obtainthird channel information, and sends the third channel information tothe second device. The third channel information includes a phasedifference between two groups of antenna ports obtained by grouping theM antenna ports. The second device generates the precoding matrix basedon the first channel information, the second channel information, andthe third channel information.

Optionally, each piece of channel information may be fed back in aflexible feedback manner, to improve channel information feedbackprecision, and reduce an information feedback amount as much aspossible.

For example, a feedback manner of the first channel information iswideband based feedback, and a feedback manner of the second channelinformation is subband based feedback. Alternatively, both a feedbackmanner of the first channel information and a feedback manner of thesecond channel information are subband based feedback, and feedbackbandwidth for the first channel information is greater than feedbackbandwidth for the second channel information.

A feedback period of the first channel information is longer than afeedback period of the second channel information.

For another example, a feedback manner of the first channel informationis wideband based feedback, and a feedback manner of the second channelinformation and a feedback manner of the third channel information aresubband based feedback. Alternatively, a feedback manner of the firstchannel information, a feedback manner of the second channelinformation, and a feedback manner of the third channel information areall subband based feedback, and feedback bandwidth for the first channelinformation is greater than feedback bandwidth for the second channelinformation and feedback bandwidth for the third channel information.

A feedback period of the first channel information is longer than afeedback period of the second channel information and a feedback periodof the third channel information.

For another example, a feedback manner of the first channel informationand a feedback manner of the second channel information are widebandbased feedback, and a feedback manner of the third channel informationis subband based feedback. Alternatively, both feedback bandwidth forthe first channel information and feedback bandwidth for the secondchannel information are greater than feedback bandwidth for the thirdchannel information.

A feedback manner of the first channel information and a feedback mannerof the second channel information are long-term feedback, and a feedbackmanner of the third channel information is short-term feedback.Alternatively, both a feedback period of the first channel informationand a feedback period of the second channel information are longer thana feedback period of the third channel information.

Optionally, the first device measures the reference signal to obtainfifth channel information and sixth channel information, and the firstdevice sends the fifth channel information and the sixth channelinformation to the second device.

The fifth channel information includes information used to indicate anamount of spatially multiplexed data from the second device to the firstdevice, and the sixth channel information includes information used toindicate channel quality of a channel from the second device to thefirst device.

The second device further generates the precoding matrix based on thefifth channel information and the sixth channel information.

The first channel information and the fifth channel information are fedback in a first subframe by using a first period, and the second channelinformation and the sixth channel information are fed back in a secondsubframe by using a second period, where the first period is not lessthan the second period; or

the first channel information and the fifth channel information are fedback in a first subframe by using a first period, the second channelinformation is fed back in a second subframe by using a second period,and the sixth channel information is fed back in a third subframe byusing a third period, where the first period is not less than the secondperiod, and the second period is not less than the third period; or

the first channel information and the fifth channel information are fedback in a first subframe by using a first period, the second channelinformation is fed back in a second subframe by using a second period,and the sixth channel information is fed back in a third subframe byusing a third period, where the first period is not less than the secondperiod, and the second period is not less than the third period; or

the fifth channel information is fed back in a first subframe by using afirst period, the first channel information is fed back in a secondsubframe by using a second period, the second channel information is fedback in a third subframe by using a third period, and the sixth channelinformation is fed back in a fourth subframe by using a fourth period,where the first period is not less than the second period, the secondperiod is not less than the third period, and the third period is notless than the fourth period.

Alternatively, when the third channel information is fed back,

the first channel information and the fifth channel information are fedback in a first subframe by using a first period, the second channelinformation and the third channel information are fed back in a secondsubframe by using a second period, and the sixth channel information isfed back in a third subframe by using a third period, where the firstperiod is not less than the second period, and the second period is notless than the third period; or

the first channel information and the fifth channel information are fedback in a first subframe by using a first period, and the second channelinformation, the third channel information, and the sixth channelinformation are fed back in a second subframe by using a second period,where the first period is not less than the second period; or

the first channel information, the second channel information, and thefifth channel information are fed back in a first subframe by using afirst period, and the third channel information and the sixth channelinformation are fed back in a second subframe by using a second period,where the first period is not less than the second period; or

the first channel information and the fifth channel information are fedback in a first subframe by using a first period, the second channelinformation is fed back in a second subframe by using a second period,and the third channel information and the sixth channel information arefed back in a third subframe by using a third period, where the firstperiod is not less than the second period, and the second period is notless than the third period; or

the first channel information and the fifth channel information are fedback in a first subframe by using a first period, the second channelinformation is fed back in a second subframe by using a second period,the third channel information is fed back in a third subframe by using athird period, and the sixth channel information is fed back in a fourthsubframe by using a fourth period, where the first period is not lessthan the second period, the second period is not less than the thirdperiod, and the third period is not less than the fourth period; or

the fifth channel information is fed back in a first subframe by using afirst period, the first channel information is fed back in a secondsubframe by using a second period, the second channel information is fedback in a third subframe by using a third period, the third channelinformation is fed back in a fourth subframe by using a fourth period,and the sixth channel information is fed back in a fifth subframe byusing a fifth period, where the first period is not less than the secondperiod, the second period is not less than the third period, the thirdperiod is not less than the fourth period, and the fourth period is notless than the fifth period.

Optionally, the first channel information, the second channelinformation, and the third channel information constitute, in thefollowing manner, the precoding matrix whose rank is 1:

${W = {\frac{1}{q}\begin{bmatrix}e_{m_{0}} & \ldots & e_{m_{N - 1}} & 0 & 0 & 0 \\0 & 0 & 0 & e_{m_{0}} & \ldots & e_{m - N - 1}\end{bmatrix}}};{where}$ ${c_{k} = \begin{bmatrix}c_{k,0} & c_{k,m} & \ldots & c_{k,{N - 1}}\end{bmatrix}^{T}},{{B_{i} = \begin{bmatrix}b_{i,0} & b_{i,m} & \ldots & b_{i,{M - 1}}\end{bmatrix}};{{and}\begin{bmatrix}e_{m_{0}} & \ldots & e_{m_{N - 1}} & 0 & 0 & 0 \\0 & 0 & 0 & e_{m_{0}} & \ldots & e_{m_{N - 1}}\end{bmatrix}}}$

corresponds to the first channel information; c_(k) is a weightedcombination factor used for performing weighted combination on the N/2ports, where c_(k,0) is used to perform weighting on an m₀ ^(th) portand an (m₀+N/2)^(th) port, c_(k,m) is used to perform weighting on anm_(N-1) ^(th) port and an (m_(N-1)+N/2)^(th) port, and c_(k,N-1) is usedto perform weighting on an m_(N-1) ^(th) port and an (m_(N-1)+N/2)^(th)port; m is an integer, and 0≤m≤M−1; φ_(n) is the phase difference thatis between the two groups of antenna ports for the reference signal andthat is indicated by the third channel information; a quantity of rowsof e_(m) ₀ ˜e_(m) _(N-1) is M; and ∥q∥ is a normalization factor.

Optionally, the first device sends, to the second device, informationused to indicate a value of N.

Alternatively, the first device receives, from the second device,information used to indicate a value of N.

Optionally,

the first channel information is used to indicate

$\begin{bmatrix}e_{m_{0}} & \ldots & e_{m_{N - 1}} & 0 & 0 & 0 \\0 & 0 & 0 & e_{m_{0}} & \ldots & e_{m_{N - 1}}\end{bmatrix}.$

Alternatively, the first channel information includes M bits. In the Mbits, an m₀ ^(th) bit to an m_(N-1) ^(th) bit are 1, and remaining bitsare 0.

Optionally, the first channel information, the second channelinformation, and the third channel information constitute, in thefollowing manner, the precoding matrix whose rank is 2:

${W = {\frac{1}{q}\begin{bmatrix}{E_{i} \cdot c_{k}} & {E_{j} \cdot c_{y}} \\{\phi_{n}{E_{i} \cdot c_{k}}} & {{- \phi_{n}}{E_{j} \cdot c_{y}}}\end{bmatrix}}};{where}$ ${c_{k} = \begin{bmatrix}c_{k,0} & \ldots & c_{k,m} & \ldots & c_{k,{R - 1}}\end{bmatrix}^{T}},{{E_{i} = \begin{bmatrix}e_{i_{0}} & \ldots & e_{i_{m}} & \ldots & e_{i_{R - 1}}\end{bmatrix}};}$ ${c_{y} = \begin{bmatrix}c_{y,0} & \ldots & c_{y,n} & \ldots & c_{y,{S - 1}}\end{bmatrix}^{T}},{{E_{j} = \begin{bmatrix}e_{j_{0}} & \ldots & e_{j_{n}} & \ldots & e_{j_{S - 1}}\end{bmatrix}};}$

R and S are positive integers, R≤M, and S≤M; and

c_(k) and c_(y) are weighted combination factors, where c_(k,0) is usedto perform weighting on an i₀ ^(th) port and an (i₀+N/2)^(th) port,c_(k,m) is used to perform weighting on an i_(m) ^(th) port and an(i_(m)+N/2)^(th) port, c_(k,R-1) is used to perform weighting on ani_(R-1) ^(th) port and an (i_(R-1)+N/2)^(th) port, c_(y,0) is used toperform weighting on a j₀ ^(th) port and a (j₀+N/2)^(th) port, c_(y,n)is used to perform weighting on a j_(n) ^(th) port and a(j_(n)+N/2)^(th) port, and c_(y,S-1) is used to perform weighting on aj_(S-1) ^(th) port and a (j_(S-1)+N/2)^(th) port; m is an integer, and0≤m≤R−1; n is an integer, and 0≤n≤S−1; φ_(n) is the phase differencethat is between the two groups of antenna ports for the reference signaland that is indicated by the third channel information; and ∥q∥ is anormalization factor.

Optionally, E_(i) is the same as E_(j), and c_(k) is different fromc_(m); or

E_(i) is different from E_(j), and c_(k) is the same as c_(m); or

E_(i) is different from E_(j), and c_(k) is different from c_(m); or

E_(i) is the same as E_(j), and c_(k) is the same as c_(m).

Optionally, the second channel information is a time delay factor.

A form that is of the precoding matrix including the first channelinformation and the second channel information and that is in timedomain is as follows:

${{W(\tau)} = {\sum\limits_{m = 0}^{N - 1}{e_{i_{m}}p_{m}{\delta \left( {\tau - \tau_{m}} \right)}}}};$

where

τ_(m) is the time delay factor corresponding to an m^(th) vector in theN first vectors.

Optionally, the second channel information includes first subchannelinformation, and the first subchannel information is used to indicatethe first factor.

The first subchannel information is not quantized.

Alternatively, first quantization is performed on the first subchannelinformation, and a quantization order of the first quantization is notgreater than a preset first-quantization order threshold.

Optionally, the second channel information includes second subchannelinformation, and the second subchannel information is used to indicatethe second factor.

The second subchannel information is not quantized.

Alternatively, second quantization is performed on the second subchannelinformation, and a quantization order of the second quantization is notless than a preset second-quantization order threshold.

According to an eighth aspect, an embodiment of the present inventionprovides a first device, and the first device has a function ofimplementing behavior of the first device in the method provided in theseventh aspect. The function may be implemented by using hardware, ormay be implemented by executing corresponding software by hardware. Thehardware or the software includes one or more modules corresponding tothe function.

In an optional implementation solution, a structure of the first deviceincludes a processor, a transmitter, and a receiver. The processor isconfigured to support the first device in performing the correspondingfunction in the method provided in the seventh aspect. The transmitteris configured to support the first device in sending a message or datain the foregoing method to a second device. The receiver is configuredto receive the message or the data in the foregoing method from thesecond device. The first device may further include a memory, and thememory is configured to couple to the processor, and stores a programinstruction and data that are necessary for the first device.

According to a ninth aspect, an embodiment of the present inventionprovides a second device, and the second device has a function ofimplementing behavior of the second device in the method provided in theseventh aspect. The function may be implemented by using hardware, ormay be implemented by executing corresponding software by hardware. Thehardware or the software includes one or more modules corresponding tothe function.

In an optional implementation solution, a structure of the second deviceincludes a transmitter, a receiver, and a processor. The receiver isconfigured to support the second device in receiving a message or datain the foregoing method from a first device. The transmitter isconfigured to support the second device in sending the message or thedata in the foregoing method to the first device. The processor isconfigured to support the first device in performing the correspondingfunction in the foregoing method. The second device may further includea memory, and the memory is configured to couple to the processor, andstores a program instruction and data that are necessary for the seconddevice.

According to a tenth aspect, an embodiment of the present inventionprovides a wireless communications system, and the wirelesscommunications system includes the first device and the second deviceaccording to any one of the seventh aspect to the ninth aspect.

According to an eleventh aspect, an embodiment of the present inventionprovides a computer storage medium. The computer storage medium isconfigured to store a computer software instruction used by the firstdevice according to any one of the seventh aspect to the tenth aspect,and includes a program designed for executing the foregoing aspects.

According to a twelfth aspect, an embodiment of the present inventionprovides a computer storage medium. The computer storage medium isconfigured to store a computer software instruction used by the seconddevice according to any one of the seventh aspect to the tenth aspect,and includes a program designed for executing the foregoing aspects.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic structural diagram of a wireless communicationssystem according to an embodiment of the present invention;

FIG. 2 is a diagram of interaction between a first device and a seconddevice according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of beam directions;

FIG. 4 to FIG. 8 are schematic diagrams of a beam selection and weightedcombination process according to an embodiment of the present invention;

FIG. 9 is a schematic diagram in which a system frequency band isdivided into a plurality of subbands;

FIG. 10A and FIG. 10B are a schematic diagram of a channel informationfeedback manner according to an embodiment of the present invention;

FIG. 11 is a schematic diagram of beams formed by antennas in onepolarization direction;

FIG. 12 is a schematic diagram of beams generated by a dual-polarizedantenna through precoding;

FIG. 13 is a schematic structural diagram of a first device according toan embodiment of the present invention; and

FIG. 14 is a schematic structural diagram of a second device accordingto an embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

To make the objectives, technical solutions, and advantages of thisapplication more understandable, the following provides detaileddescriptions. The detailed descriptions provide various implementationsof an apparatus and/or a method by using block diagrams, flowcharts,and/or examples. These block diagrams, flowcharts, and/or examplesinclude one or more functions and/or operations. Persons skilled in theart may understand that each function and/or operation in the blockdiagrams, the flowcharts, and/or the examples can be performedindependently and/or jointly by using various hardware, software, andfirmware, or any combination of hardware, software, and firmware.

In the embodiments of the present invention, a second device sends areference signal to a first device. The first device performs channelestimation based on the received reference signal, generates channelinformation, and feeds back the channel information to the seconddevice. The second device determines a precoding matrix based on thereceived channel information, and sends data to the first device basedon the determined precoding matrix.

In the embodiments of the present invention, solutions can becategorized into Solution 1 and Solution 2, based on different channelinformation fed back by the first device and different manners ofconstituting the precoding matrix.

In Solution 1, reference signals sent by the second device are areference signal on which beamforming is not performed and a referencesignal on which beamforming is performed. The reference signal on whichbeamforming is not performed corresponds to H=1, and the referencesignal on which beamforming is performed corresponds to H>1. For H>1,different reference signal resource port groups correspond to differentbeam directions, and antenna ports in one reference signal resource portgroup correspond to a same beam direction. For example, there are H=4groups, and each group has eight antenna ports. A beam direction 1 isobtained by performing same beamforming on all eight antenna ports in afirst reference signal resource port group, a beam direction 2 isobtained by performing same beamforming on all eight antenna ports in asecond reference signal resource port group, and so on. The first deviceperforms channel estimation based on the received reference signal, andfeeds back, to the second device, second channel information of aweighted combination factor used for performing weighted combination onM first vectors. The M first vectors may be vectors included in a codeword W₁ corresponding to the foregoing precoding matrix W. In this way,when generating the precoding matrix, the second device may performweighted combination on the M first vectors based on the weightedcombination factor indicated by the received second channel information,instead of selecting only one vector from a plurality of vectors, sothat the generated precoding matrix is more precise, thereby improving alink adaptation capability of the second device for sending data, andimproving system performance.

In Solution 2, if the reference signal sent by the second device is areference signal on which beamforming is performed, the first deviceperforms channel estimation based on the received reference signal, andfeeds back, to the second device, second channel information of aweighted combination factor used for performing weighted combination onM antenna ports for the reference signal. In this way, when generatingthe precoding matrix, the second device may perform weighted combinationon the M antenna ports based on the weighted combination factorindicated by the received second channel information, so that arelatively precise precoding matrix can also be generated, thereby alsoimproving a link adaptation capability of the second device for sendingdata, and improving system performance.

The embodiments of the present invention are described below in detailwith reference to the accompanying drawings.

First, composition of a wireless communications system to which bothSolution 1 and Solution 2 are applicable is described.

FIG. 1 is a schematic structural diagram of a wireless communicationssystem according to an embodiment of the present invention. As shown inFIG. 1, the wireless communications system includes a first device 101and a second device 102.

The second device 102 sends a reference signal to the first device 101.The first device 101 performs channel estimation based on the referencesignal received from the second device 102, and sends, to the seconddevice 102, channel information used to indicate a channel estimationresult. The second device 102 sends data to the first device 101 basedon the received channel information.

The foregoing process of interaction between the first device 101 andthe second device 102 may be shown in FIG. 2.

The first device 101 may be a network device such as a base station, andthe second device 102 may be a terminal device. Alternatively, the firstdevice 101 may be a terminal device, and the second device 102 may be anetwork device. Alternatively, both the first device 101 and the seconddevice 102 are terminal devices. Alternatively, both the first device101 and the second device 102 are network devices.

Provided that the second device 102 sends a reference signal to thefirst device 101, and that the first device 101 performs channelestimation based on the reference signal and feeds back channelinformation, Solution 1 or Solution 2 provided in the embodiments of thepresent invention may be used to report the channel information and senddata, to obtain a more precise channel estimation result and improvelink adaptation performance.

In addition, regardless of a duplex manner used when the first device101 and the second device 102 communicate with each other, such as theforegoing FDD duplex manner or a time division duplex (TDD) duplexmanner, Solution 1 or Solution 2 provided in the embodiments of thepresent invention may be used, to obtain a precise channel estimationresult and improve link adaptation performance.

A communications standard for communication between the first device 101and the second device 102 may include but is not limited to GlobalSystem for Mobile Communications (GSM), Code Division Multiple Access(CDMA) IS-95, Code Division Multiple Access (CDMA) 2000, TimeDivision-Synchronous Code Division Multiple Access (TD-SCDMA), WidebandCode Division Multiple Access (WCDMA), Time Division Duplex-Long TermEvolution (TDD LTE), Frequency Division Duplex-Long Term Evolution (FDDLTE), Long Term Evolution-Advanced (LTE-advanced), a personal handyphonesystem (PHS), Wireless Fidelity (WiFi) regulated by the 802.11 series ofprotocols, Worldwide Interoperability for Microwave Access (WiMAX), andvarious evolved wireless communications systems in the future.

The terminal device may be a wireless terminal. The wireless terminalmay be a device that provides voice and/or data connectivity for a user,a handheld device with a wireless connection function, or anotherprocessing device connected to a wireless modem. The wireless terminalmay communicate with one or more core networks by using a radio accessnetwork (for example, RAN). The wireless terminal may be a mobileterminal such as a mobile phone (also referred to as a “cellular” phone)and a computer with a mobile terminal, for example, may be a portable,pocket-sized, handheld, computer built-in, or in-vehicle mobileapparatus that exchanges voice and/or data with the radio accessnetwork. For example, the wireless terminal may be a device such as apersonal communications service (PCS) phone, a cordless phone, a SessionInitiation Protocol (SIP) phone, a wireless local loop (WLL) station, ora personal digital assistant (PDA). The wireless terminal may also bereferred to as a subscriber unit, a subscriber station, a mobilestation, a mobile, a remote station, an access point, a remote terminal,an access terminal), a user terminal, a user agent, a user device, oruser equipment.

The network device may include a base station, or a radio resourcemanagement device for controlling a base station, or may include a basestation and a radio resource management device for controlling the basestation. The base station may be a macro base station or a micro basestation, such as a small cell or a pico cell. Alternatively, the basestation may be a home base station, such as a home NodeB (HNB) or a homeevolved NodeB (HeNB). The base station may also include a relay node(relay) and the like.

For example, in an LTE system such as TDD LTE, FDD LTE, or LTE-A, thenetwork device may be an evolved NodeB (eNodeB), and the terminal devicemay be UE. In a TD-SCDMA system or a WCDMA system, the network devicemay include a NodeB and/or a radio network controller (RNC), and theterminal device may be UE. In a GSM system, the network device mayinclude a base transceiver station (BTS) and/or a base stationcontroller (BSC), and the terminal device may be a mobile station (MS).In a WiFi system, the network device may include an access point (AP)and/or an access controller (AC), and the terminal device may be astation (STA).

Solution 1 and Solution 2 are separately described below with referenceto the wireless communications system shown in FIG. 1.

Solution 1

In Solution 1, channel information sent by a first device 101 to asecond device 102 is shown in the following Table 1.

TABLE 1 Channel information in Solution 1 Channel information MeaningDescription First channel Identification information information of Mfirst vectors Second channel Weighted combination Used for performingweighted combination information factor on N first vectors in the Mfirst vectors, and including a first factor and/or a second factor Firstfactor: amplitude factor Second factor: phase factor or time delayfactor Third channel Phase difference between information two groups ofantenna ports for a reference signal Fourth channel Selectioninformation used information to select N first vectors from the M firstvectors

I. First Vector and Channel Information

The M first vectors are M first vectors in a universal set of firstvectors. A value of M may be preset, for example, may be predefined in acommunications standard followed by both the first device 101 and thesecond device 102 when the first device 101 and the second device 102communicate with each other, or may be notified by the first device 101to the second device 102 before the first device 101 sends the firstchannel information to the second device 102, or may be notified by thesecond device 102 to the first device 101 before the second device 102sends the reference signal.

Herein, the universal set of first vectors is denoted as B=[b₀ b₁ . . .b_(L-1)], where L is a positive integer, and is a quantity of firstvectors included in the universal set of first vectors.

In the universal set of first vectors, each first vector may representone direction of a beam sent by the second device 102 to the firstdevice 101.

Referring to FIG. 3, it is assumed that L=12. In this case, B=[b₀ b₁ . .. b₁₁], and vectors b₀ b₁ . . . b₁₁ respectively represent 12 beamdirections in FIG. 3.

The first device 101 sends the first channel information to the seconddevice 102 to notify the second device 102 of a beam direction fromwhich the first device 101 expects to receive the reference signal, andsends the second channel information to the second device 102 to notifythe second device 102 that a combined beam that the first device 101expects to receive is a weighted combination adjustment amount ofamplitude and phase weighting of each corresponding beam direction (eachfirst vector) in the first channel information.

When determining the first channel information and the second channelinformation, the first device 101 may measure the reference signal toobtain a channel estimation result; determine a beam direction in whichthe second device 102 needs to send data when a maximum received signalto noise ratio (SNR) can be reached or a capacity is maximized, and aweighted combination adjustment amount of amplitude and phase weightingin each beam direction in which the second device 102 needs to senddata; and then notify the second device 102 by using the first channelinformation and the second channel information.

It is still assumed that L=12, and B=[b₀ b₁ . . . b₁₁]. If a dual stagecodebook structure W=W₁×W₂ is used for a precoding matrix, M=4, and thefirst device 101 selects first four first vectors: b₀, b₁, b₂, and b₃,the precoding matrix W m be indicated as:

$\begin{matrix}{{{W = {{\frac{1}{q}\begin{bmatrix}b_{0} & b_{1} & b_{2} & b_{3} & 0 & 0 & 0 & 0 \\0 & 0 & 0 & 0 & b_{0} & b_{1} & b_{2} & b_{3}\end{bmatrix}}\begin{bmatrix}c_{k} \\{\phi_{n}c_{k}}\end{bmatrix}}};{where}}\mspace{20mu} {{W_{1} = \begin{bmatrix}b_{0} & b_{1} & b_{2} & b_{3} & 0 & 0 & 0 & 0 \\0 & 0 & 0 & 0 & b_{0} & b_{1} & b_{2} & b_{3}\end{bmatrix}},{and}}\text{}\mspace{20mu} {W_{2} = {\begin{bmatrix}c_{k} \\{\phi_{n}c_{k}}\end{bmatrix}.}}} & {{Formula}\mspace{14mu} 4}\end{matrix}$

The first channel information is used to identify b₀, b₁, b₂, and b₃.

The second channel information is c_(k)=p_(k)*α_(k), where

${{p_{k} \in \left\{ {p_{0},p_{1},p_{2},p_{3}} \right\}} = \left\{ {\frac{1}{4},\frac{3}{4},\frac{1}{8},\frac{7}{8}} \right\}},{\alpha_{k} \in \left\{ {\alpha_{0},\alpha_{1},\alpha_{2},\alpha_{3}} \right\} \in \left\{ {1,{- 1},j,{- j}} \right\}},$

p_(k) is an amplitude factor, α_(k) is a phase factor, p₀ is used toperform amplitude weighting on b₀, α₀ is used to perform phase weightingon b₀, and so on. ∥q∥ is a normalization factor. A value of theamplitude factor and a value of the phase factor herein are merelyexamples. An entire beam selection and weighted combination process maybe shown in FIG. 4. Beams b₀, b₁, b₂, and b₃ are selected by using W₁,phase weighting is performed on the beams by using a, to obtain vectorsb′₀, b′₁, b′₂, and b′₃; after phase weighting. Beams b″₀, b″₁, b″₂, andb″₃; are obtained by performing amplitude weighting by using p_(k), andthen vectors b″₀, b″₁, b″₂, and b″₃ are combined to obtain one combinedvector. The vector corresponds to one combined beam. In FIG. 4, phaseweighting is performed before amplitude weighting, and FIG. 4 herein ismerely schematic. Actually, amplitude weighting may be performed beforephase weighting, or amplitude weighting and phase weighting may besimultaneously performed. Optionally, if phase weighting amounts for allvectors are the same, the first device 101 may feed back only one phasefactor for a plurality of beams. Likewise, if amplitude weighting valuesfor all vectors are the same, the first device 101 may feed back onlyone amplitude factor for a plurality of vectors, such as p shown in FIG.5.

The first vectors may be vectors included in a code word W₁corresponding to the foregoing precoding matrix W, and may be DiscreteFourier Transform (DFT) vectors, for example, in a form shown in thefollowing formula 5:

$\begin{matrix}{{DFT} = {\begin{bmatrix}b_{0} & b_{1} & \ldots & b_{L - 1}\end{bmatrix} = {\quad\begin{bmatrix}1 & 1 & \ldots & 1 \\1 & e^{j\frac{2\pi}{L}} & \ldots & e^{j\frac{2\pi}{L}{({L - 1})}} \\\vdots & \vdots & \ldots & \vdots \\1 & e^{j\frac{2\pi}{L}{({I - 1})}} & \ldots & e^{j\frac{2\pi}{L}{({I - 1})}{({L - 1})}}\end{bmatrix}}}} & {{Formula}\mspace{14mu} 5}\end{matrix}$

L and I are positive integers, and L indicates a quantity of firstvectors included in the universal set of first vectors, in other words,indicates a quantity of beams that are in different beam directions andthat can be sent by the second device 102. I is a dimension of the firstvector, is a quantity of antenna ports for the reference signal when asingle-polarization manner is used for an antenna used by the seconddevice 102 to send the reference signal, and is half of a quantity ofantenna ports for the reference signal when a dual-polarization manneris used for an antenna used by the second device 102 to send thereference signal. The antenna port for the reference signal is anantenna port used by the second device 102 to send the reference signal.

For example, if L=32, and I=4,

B=[b ₀ b ₁ . . . b ₃₁]  Formula 6; where

${\lbrack B\rbrack_{{1 + i},{1 + l}} = e^{j\frac{2\pi \; {il}}{32}}},{i = 0},1,2,3,{l = 0},1,\ldots \;,31.$

The second channel information may include only the first factor, orinclude only the second factor, or include both the first factor and thesecond factor.

For example, if the second channel information includes only the firstfactor, when weighted combination is performed on the M first vectors,phase weighting may not be performed on the vectors, or phase weightingis performed on the M first vectors based on a preset same phaseweighting amount, or phase weighting is performed based on presetdifferent phase weighting amounts for different first vectors. Becausethe phase weighting amount is preset, the first device 101 does not needto feed back the phase weighting amount to the second device 102.

For another example, if the second channel information includes only thesecond factor, when weighted combination is performed on the M firstvectors, weighting may be performed on the first vectors based on apreset same amplitude value, or weighting is separately performed on thefirst vectors based on preset different amplitude factors for differentfirst vectors. Because the amplitude value is preset, the first device101 does not need to feed back the amplitude value to the second device102.

The phase factor and the time delay factor in the second factor areactually used to respectively perform phase weighting on the firstvector from perspectives of frequency domain and time domain. A timedelay in time domain is equivalent to phase weighting in frequencydomain. Therefore, if the phase factor needs to be fed back, only eitherof the phase factor and the time delay factor needs to be fed back.Optionally, a feedback manner of the phase factor is subband basedfeedback, and a feedback manner of the time delay factor is widebandbased feedback.

The third channel information is used to indicate the phase differencebetween the two groups of antenna ports for the reference signal. Forexample, the two groups of antenna ports have different polarizationdirections. In this case, the phase difference indicates a phasedifference between the two groups of antenna ports having differentpolarization directions. For example, there are eight antenna ports intotal, four antenna ports are horizontally polarized, and the other fourantenna ports are vertically polarized. In this case, the third channelinformation is used to indicate a phase difference between the twogroups of antenna ports that are respectively horizontally polarized andvertically polarized.

The M first vectors are some first vectors in the universal set of firstvectors. In an optional implementation, the universal set of firstvectors is divided into K vector groups, and K is a positive integer.The M first vectors belong to X vector groups, and the X vector groupsare some or all of the K vector groups. K is a positive integer, and Xis a positive integer not greater than K.

Different vector groups in the K vector groups include or do not includea same first vector.

For example, the universal set of first vectors is B=[b₀ b₁ . . . b₃₁].Vectors b₀ b₁ . . . b₃₁ are all 32 first vectors.

A grouping manner in which different vector groups in the K vectorgroups do not include a same first vector may be as follows: b₀ b₁ . . .b₃₁ are grouped into eight groups (K=8), and each group has four firstvectors. For example, b₀, b₁, b₂, and b₃ forms a vector group, b₄, b₅,b₆, and b₇ forms a vector group, and so on.

A grouping manner in which different vector groups in the K vectorgroups include a same first vector may be as follows: b₀ b₁ . . . b₃₁are grouped into 16 groups (K=16), and each group has four firstvectors. For example, b₀, b₁, b₂, and b₃ forms a vector group, b₂, b₃,b₄, and b₅ forms a vector group, and so on.

The following is also a grouping manner in which different vector groupsin the K vector groups include a same first vector: The 32 first vectorsare divided into 16 groups in total, a group number k is 0 to 15, andK=16.

X ^((k))∈{[b _(2k mod 32) b _((2k+1)mod 32) b _((2k+mod 32) b_((2k+3)mod 32)]: k=0,1, . . . ,15}  Formula 7;

where

$W_{1}^{(k)} = {\begin{bmatrix}X^{(k)} & 0 \\0 & X^{(k)}\end{bmatrix}.}$

If the M first vectors include two vector groups X^((i)) and X^((j)),

$W_{1} = {\begin{bmatrix}X^{(i)} & X^{(j)} & 0 & 0 \\0 & 0 & X^{(i)} & X^{(j)}\end{bmatrix}.}$

In this case,

$\begin{matrix}{{W = {{\frac{1}{q}\begin{bmatrix}b_{i,0} & b_{i,1} & b_{i,2} & b_{i,3} & b_{j,0} & b_{j,1} & b_{j,2} & b_{j,3} & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 \\0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & b_{i,0} & b_{i,1} & b_{i,2} & b_{i,3} & b_{j,0} & b_{j,1} & b_{j,2} & b_{j,3}\end{bmatrix}}W_{2}}};} & {{Formula}\mspace{14mu} 8}\end{matrix}$

where

b_(i,0), b_(i,1), b_(i,2), and b_(i,3) are four vectors in a vectorgroup i, b_(j,0), b_(j,1), b_(j,2), and b_(j,3) are four vectors in avector group j, the eight vectors together constitute the M firstvectors, M=8, and ∥q∥ is a normalization factor, and is equal to asquare root of a quadratic sum of modulus of all elements in W, so thata power sum of all beams is 1.

If the foregoing grouping manner is used, the first channel informationincludes a group number of each of X vector groups including the M firstvectors in the K vector groups, for example, information used toindicate the foregoing vector group numbers i and j. In such a feedbackmanner, a quantity of information bits of the first channel informationcan be reduced.

It is assumed that the first device 101 selects the vector group i andthe vector group j, W₂ is used to separately perform weighting, forexample, including both amplitude weighting and phase weighting, on allfirst vectors in W₁ ^((i)) and W₁ ^((j)). In this case, an expression ofW₂ may be:

$\begin{matrix}{{{W_{2} = \begin{bmatrix}c_{i} \\c_{j} \\{\phi_{n}c_{i}} \\{\phi_{n}c_{j}}\end{bmatrix}};{where}}{{c_{i} = \begin{bmatrix}c_{i,0} & c_{i,1} & c_{i,2} & c_{i,3}\end{bmatrix}^{T}},{and}}\text{}{c_{j} = {\begin{bmatrix}c_{j,0} & c_{j,1} & c_{j,2} & c_{j,3}\end{bmatrix}^{T}.}}} & {{Formula}\mspace{14mu} 9}\end{matrix}$

c_(i,k)=p_(i,k)*α_(i,k). For example,

${p_{i,k} \in \left\{ {\frac{1}{4},\frac{3}{4},\frac{1}{8},\frac{7}{8}} \right\}},$

and α_(i,k)∈{1, −1, j, −j}, where α_(i,k) is a phase adjustment amountbefore the first vectors are combined, the given {1,−1, j,−j} is merelyan example, and the phase adjustment amount is not limited to the fourvalues; p_(i,k) is an amplitude adjustment amount before the firstvectors are combined; and first vectors in a same vector group may havea same amplitude factor and a same weighting factor.

In an application scenario of grouping the first vectors, a plurality ofbeams may be divided into different beam clusters. In practice, thefirst device 101 may select, from the plurality of clusters, a beamcluster in which received signal strength or a power value of a receivedreference signal is relatively large. In this way, after the firstdevice 101 feeds back the channel information, the second device 102 mayseparately send data on beams in the plurality of beam clusters, and thefirst device 101 may receive downlink data on a plurality of beams withbetter receiving quality, so that performance is better.

Referring to FIG. 6, first, two groups of first vectors are selected. Avector group 1 includes four first vectors: b₀, b₁, b₂, and b₃, andbeams represented by the four vectors constitute a relatively strongbeam cluster: cluster 1. A vector group 2 includes four first vectors:b₄, b₅, b₆, and b₇, and beams represented by the four vectors constitutea relatively strong beam cluster: cluster 2. W₁ ⁽¹⁾ is used to selectthe cluster 1, and W₁ ⁽²⁾ is used to select the cluster 2. α₀, α₁, α₂,α₃ are respectively used to perform phase weighting on the beamsrepresented by the first vectors b₀, b₁, b₂, and b₃. First vectorsobtained after phase weighting are respectively b′₀, b′₁, b′₂, and b′₃.α₄, α₅, α₆, α₇, are respectively used to perform phase weighting on thebeams represented by the first vectors b₄, b₅, b₆, and b₇. First vectorsobtained after phase weighting are respectively b′₄, b′₅, b′₆, and b′₇.In FIG. 6, amplitude factors of all the vectors in the vector group 1(namely, the cluster 1) are p₀, and amplitude factors of all the vectorsin the vector group 2 (namely, the cluster 2) are p₁. Therefore, whensending the second channel information, the first device 101 may feedback only one amplitude factor p₀ for all the first vectors in thevector group 1, and feed back only one amplitude factor p₁ for all thefirst vectors in the vector group 2.

Optionally, the first device 101 may further send, to the second device102, information used to indicate a value of X, to be specific, aquantity of vector groups to which the M first vectors belong.Alternatively, the first device 101 receives, from the second device102, information used to indicate a value of X.

In the foregoing example, quantities of first vectors included indifferent vector groups are the same. However, in actual implementation,quantities of first vectors included in different vector groups may notbe the same, as shown in FIG. 7.

In an optional implementation, different vector groups in the foregoingX vector groups correspond to same second channel information. For thedifferent vector groups, the first device 101 sends only one same pieceof second channel information to the second device 102. In this way, abit quantity of the second channel information can be reduced.

In another optional implementation, different vector groups correspondto different second channel information. For the different vectorgroups, the first device 101 needs to separately feed back the secondchannel information.

Referring to Table 1, the second channel information is used to performweighted combination on the N first vectors in the M first vectors. Inthis case, there are the following cases:

Case 1: If M=N, weighted combination is performed on all the M firstvectors, and the second channel information needs to include a weightingfactor of each of the M first vectors.

Case 2: If N<M, the N first vectors may be selected from the M firstvectors in two manners:

The weighted combination factor indicated by the second channelinformation includes an element 0.

For example, an amplitude factor corresponding to a specific firstvector in the M first vectors is 0. In this case, the first vector whoseamplitude factor is 0 is removed from the M first vectors. In otherwords, the first vector corresponding to the amplitude factor is notselected.

The fourth channel information is sent to instruct to select the N firstvectors from the M first vectors.

If the first device 101 sends the fourth channel information, whensending the second channel information, the first device 101 does notneed to send a weighted combination factor of each of the M firstvectors, but sends only a weighted combination factor of each of the Nselected first vectors.

If the M first vectors include X vector groups, each of the X vectorgroups may have corresponding fourth channel information, so as toselect a first vector from the vector group. A same quantity of firstvectors or different quantities of first vectors may be selected fromdifferent vector groups.

Referring to FIG. 8, column selection is performed inside each vectorgroup. To be specific, weighted combination is performed after a firstvector is selected. In addition, different quantities of columns may beselected from all vector groups. For example, for W₁ ⁽¹⁾, two firstvectors are selected (in other words, two beams are selected). For W₁⁽²⁾, three first vectors are selected (in other words, three beams areselected). Then, phase weighting and amplitude adjustment are separatelyperformed on the two beams and the three beams.

The first vector and each piece of channel information are describedabove. How to construct a precoding matrix based on the channelinformation is described below.

II. Construction of a Precoding Matrix

1. The precoding matrix is constituted based on the first channelinformation, the second channel information, and the third channelinformation, and a rank is 1.

The precoding matrix W is:

${W = {{\frac{1}{q\; }\begin{bmatrix}B_{i} & 0 \\0 & B_{i}\end{bmatrix}}\begin{bmatrix}c_{k} \\{\phi_{n}c_{k}}\end{bmatrix}}};{where}$ ${c_{k} = \begin{bmatrix}c_{k,0} & \ldots & c_{k,m} & \ldots & c_{k,{M - 1}}\end{bmatrix}^{T}},{B_{i} = \begin{bmatrix}b_{i,0} & \ldots & b_{i,m} & \ldots & b_{i,{M - 1}}\end{bmatrix}}$

B_(i) is the M first vectors; c_(k) is the weighted combination factor,where c_(k,0) is used to perform weighting on b_(i,0), c_(k,m) is usedto perform weighting on b_(i,m), and c_(k,M-1) is used to performweighting on b_(i,M-1); m is an integer, and 0≤m≤M; φ_(n) is the phasedifference that is between the two groups of antenna ports for thereference signal and that is indicated by the third channel information;and J is a normalization factor.

If the M first vectors are grouped, B_(i) is a vector group whose groupnumber is i in the K vector groups. In this case, the first channelinformation includes information used to indicate i. If B_(i) isindicated as B_(i)=[B_(i) ₀ . . . B_(i) _(x) . . . B_(i) _(X-1) ], wherethe X vector groups B_(i) ₀ . . . B_(i) _(x) . . . B_(i) _(X-1) arevector groups whose group numbers are sequentially i₀ to i_(X-1) in theK vector groups, x is an integer, 0≤x≤X−1, X is a positive integer, allfirst vectors in the K vector groups constitute a universal set of thefirst vectors, and K is a positive integer, the first channelinformation includes information used to separately indicate i₀ toi_(X-1).

2. The precoding matrix is constituted based on the first channelinformation, the second channel information, the third channelinformation, and the fourth channel information, and a rank is 1.

The precoding matrix W is:

${W = {{{\frac{1}{q\; }\begin{bmatrix}B_{i} & 0 \\0 & B_{i}\end{bmatrix}}\begin{bmatrix}e_{m_{0}} & \ldots & e_{m_{N - 1}} & 0 & 0 & 0 \\0 & 0 & 0 & e_{m_{0}} & \ldots & e_{m_{N - 1}}\end{bmatrix}}\begin{bmatrix}c_{k} \\{\phi_{n}c_{k}}\end{bmatrix}}};{where}$ $\mspace{20mu} {{c_{k} = \begin{bmatrix}c_{k,0} & \ldots & c_{k,m} & \ldots & c_{k,{N - 1}}\end{bmatrix}^{T}},{and}}$ $\mspace{20mu} {{B_{i} = \begin{bmatrix}b_{i,0} & \ldots & b_{i,m} & \ldots & b_{i,{M - 1}}\end{bmatrix}};}$

and

B_(i) is the M first vectors; c_(k) is the weighted combination factorused for performing weighted combination on the N first vectors, wherec_(k,0) is used to perform weighting on b_(i,m) ₀ , c_(k,m) is used toperform weighting on b_(i,m) _(m) , . . . , and c_(k,N-1) is used toperform weighting on b_(i,m) _(N-1) ; m is an integer, and 0≤m≤M−1;φ_(n) is the phase difference that is between the two groups of antennaports for the reference signal and that is indicated by the thirdchannel information; a quantity of rows of e_(m) ₀ ˜e_(m) _(N-1) is M,and the fourth channel information is information used to indicate m₀ tom_(N-1); and ∥q∥ is a normalization factor.

Optionally, the first device 101 sends, to the second device 102,information used to indicate a value of N.

Alternatively, the first device 101 receives, from the second device102, information used to indicate a value of N.

Optionally, the fourth channel information may be used to indicate

$\begin{bmatrix}e_{m_{0}} & \ldots & e_{m_{N - 1}} & 0 & 0 & 0 \\0 & 0 & 0 & e_{m_{0}} & \ldots & e_{m_{N - 1}}\end{bmatrix}.$

Alternatively, the fourth channel information includes M bits. In the Mbits, an m₀ ^(th) bit to an m_(N-1) ^(th) bit are 1, and remaining bitsare 0.

3. The precoding matrix is constituted based on the first channelinformation, the second channel information, and the third channelinformation, and a rank is 2.

The precoding matrix W is:

${W = {\frac{1}{q\; }\begin{bmatrix}{B_{i} \cdot c_{k}} & {B_{j} \cdot c_{y}} \\{\phi_{n}{B_{i} \cdot c_{k}}} & {{- \phi_{n}}{B_{j} \cdot c_{y}}}\end{bmatrix}}};{where}$ ${c_{k} = \begin{bmatrix}c_{k,0} & \ldots & c_{k,m} & \ldots & c_{k,{R - 1}}\end{bmatrix}^{T}},{{B_{i} = \begin{bmatrix}b_{i,0} & \ldots & b_{i,m} & \ldots & b_{i,{R - 1}}\end{bmatrix}};}$ ${c_{y} = \begin{bmatrix}c_{y,0} & \ldots & c_{y,n} & \ldots & c_{y,{S - 1}}\end{bmatrix}^{T}},{{B_{j} = \begin{bmatrix}b_{j,0} & \ldots & b_{j,n} & \ldots & b_{j,{S - 1}}\end{bmatrix}};}$

R and S are positive integers, R≤M, S≤M, and B_(i) and B_(j) jointlyconstitute the M first vectors; and

c_(k) and c_(y) are weighted combination factors, where c_(k,0) is usedto perform weighting on b_(i,0), c_(k,m) is used to perform weighting onb_(i,m), c_(k,R-1) is used to perform weighting on b_(i,R-1), c_(y,0) isused to perform weighting on b_(j,0), c_(y,n) is used to performweighting on b_(j,n), and c_(y,S-1) is used to perform weighting onb_(j,S-1); m is an integer, and 0≤m≤R−1; n is an integer, and 0≤n≤S−1;φ_(n) is the phase difference that is between the two groups of antennaports for the reference signal and that is indicated by the thirdchannel information; and ∥q∥ is a normalization factor.

B_(i) is the same as B_(j), and c_(k) is different from c_(m); or

B_(i) is different from B_(j), and c_(k) is the same as c_(m); or

B_(i) is different from B_(j), and c_(k) is different from c_(m); or

B_(i) is the same as B_(j), and c_(k) is the same as c_(m).

4. If the second channel information is a time delay factor, a form thatis of the precoding matrix including the first channel information andthe second channel information and that is in time domain is as follows:

${{W(\tau)} = {\sum\limits_{m = 0}^{N - 1}{b_{i,m}p_{m}{\delta \left( {\tau - \tau_{m}} \right)}}}};$

where

τ_(m) is the time delay factor corresponding to an m^(th) vector in theN first vectors.

III. Two-Dimension Codebook

The foregoing description in Solution 1 may be used when transmitantennas of the second device 102 are a linear array, and a codebook ofthe precoding matrix is a one-dimension (D) codebook. Solution 1 mayalso be used when transmit antennas of the second device 102 include anantenna array with a horizontal direction and a vertical direction. Inthis case, a codebook of the precoding matrix is a 2D codebook. In acase of the 2D codebook, the precoding matrix may be still indicated asW=W₁W₂.

However, different from the 1D codebook, each first vector in W₁ is aKronecker product of vectors in two dimensions. The vectors in twodimensions are respectively referred to as a “second vector” and a“third vector”.

B_(i) is the M first vectors, and B_(i)=[b_(i,0) b_(i,m) . . .b_(i,M-1)].

Each first vector in B_(i) is a Kronecker product of a second vector ina second vector group and a third vector in a third vector group:b_(i,m)=a_(p,m) ₁ ⊗d_(t,m) ₂ , where

b_(i,m) is the first vector, a_(p,m) ₁ is a second vector whose numberis m₁ in the second vector group whose number is p, and d_(t,m) ₂ is athird vector whose number is m₂ in the third vector group whose numberis t.

The first channel information includes first subchannel information andsecond subchannel information.

The first subchannel information is used to indicate p, and the secondsubchannel information is used to indicate t.

${a_{p,m_{1}} = \begin{bmatrix}1 & e^{j\; 2\; \pi \frac{({{p*S_{1}} + m_{1}})}{N_{1}Q_{1}}} & \ldots & e^{j\; 2\; \pi \frac{{{({N_{1} - 1})})}{({{p*S_{1}} + m_{1}})}}{N_{1}Q_{1}}}\end{bmatrix}^{T}};$

where

N₁ is a quantity of first-dimension antenna ports (for example, theforegoing horizontal antennas) in an antenna array, Q₁ is a factor usedfor oversampling DFT vectors that constitute a code word set offirst-dimension antennas, and s₁ is a positive integer.

${d_{t,m_{2}} = \begin{bmatrix}1 & e^{j\; 2\; \pi \frac{({{t*S_{2}} + m_{2}})}{N_{2}Q_{2}}} & \ldots & e^{j\; 2\; \pi \frac{{{({N_{1} - 1})})}{({{p*S_{2}} + m_{2}})}}{N_{2}Q_{2}}}\end{bmatrix}^{T}};$

where

N₂ is a quantity of second-dimension antenna ports in the antenna array,Q₂ is a factor used for oversampling DFT vectors that constitute a codeword set of second-dimension antennas, and s₂ is a positive integer.

Optionally, a quantity of second vector groups is greater than or equalto 2, and a quantity of third vector groups is equal to 1; or

a quantity of third vector groups is greater than or equal to 2, and aquantity of second vector groups is equal to 1; or

a quantity of third vector groups is equal to 1, and a quantity ofsecond vector groups is equal to 1.

Optionally, the second vector and the third vector are DFT vectors.

A quantity of vectors included in a universal set of second vectors anda quantity of vectors included in a universal set of third vectors aremutually independently configured.

IV. Cases of Grouping the Antenna Ports for the Reference Signal

The foregoing description in Solution 1 is applicable to a case in whichthe antenna ports for the reference signal are not grouped. In anotherpossible case, the reference signal is on S antenna ports, and the Santenna ports belong to H reference signal resource port groups, where His an integer greater than or equal to 1. The reference signal is areference signal on which beamforming is performed.

A dimension of the first vector is a quantity of antenna ports in eachreference signal resource port group when a single-polarization manneris used for an antenna used by the second device 102 to send thereference signal. A dimension of the first vector is half of a quantityof antenna ports in each reference signal resource port group when adual-polarization manner is used for an antenna used by the seconddevice 102 to send the reference signal.

It can be learned that when H=1, in other words, the antenna ports forthe reference signal are not grouped, that is, the case in Solution 1,Solution 1 is applicable to a case in which a reference signal on whichbeamforming is not performed.

For example, a quantity of antenna ports for the reference signal is 32,H=1, there is only one reference signal resource port group, and aquantity of ports in the reference signal resource port group is 32. Inthis case, a dimension of the first vector is 32 or 16.

For another example, a quantity of antenna ports for the referencesignal is 32, and H=4. In this case, the 32 antenna ports are groupedinto four reference signal resource port groups, and a quantity ofantenna ports in each reference signal resource port group is 8. Forexample, antenna ports in a first reference signal resource port groupare a port 0 to a port 7, antenna ports in a second reference signalresource port group are a port 8 to a port 15, antenna ports in a thirdreference signal resource port group are a port 16 to a port 23, andantenna ports in a fourth reference signal resource port group are aport 24 to a port 31. In this case, a dimension of the first vector is 8(single polarization) or 4 (dual polarization).

Optionally, the first device 101 further measures the reference signalto obtain seventh channel information, and sends the seventh channelinformation to the second device.

The seventh channel information includes identification information usedto select Y reference signal resource port groups from the H referencesignal resource port groups.

The seventh channel information is not fed back in a same subframe asother channel information, in other words, is independently fed back. Inaddition, a feedback period of the seventh channel information isgreater than or equal to a feedback period of the other channelinformation.

The M first vectors may be obtained by performing measurement based onthe Y reference signal resource port groups selected from the Hreference signal resource port groups, where Y is a positive integer.

Optionally, the M first vectors correspond to X vector groups, eachvector group corresponds to one of the Y reference signal resource portgroups, and X=Y.

Alternatively, the M first vectors correspond to X vector groups, atleast two vector groups correspond to one of the Y reference signalresource port groups, and X>Y.

When the first device 101 feeds back the seventh channel information tothe second device 102, it is assumed that B_(i)=[B_(i) ₀ . . . B_(i)_(x) . . . B_(i) _(X-1) ].

The X vector groups B_(i) ₀ . . . B_(i) _(x) . . . B_(i) _(X-1) arevector groups whose group numbers are sequentially i₀ to i_(X-1) in theK vector groups, x is an integer, 0≤x≤X−1, and X is a positive integer.

All the first vectors in the K vector groups constitute the universalset of the first vectors, and K is a positive integer.

The first channel information includes information separately used toindicate i₀ to i_(X-1).

B_(i) ₀ is obtained by the first device 101 by measuring a referencesignal sent on a first reference signal resource port group in the Yreference signal resource port groups in an H reference signal resourceport group. B_(i) _(x) is obtained by the first device 101 by measuringa reference signal sent on an x^(th) reference signal resource portgroup in the Y reference signal resource port groups in the H referencesignal resource port group. B_(i) _(x) is obtained by the first device101 by measuring a reference signal sent on an X^(th) reference signalresource port group in the Y reference signal resource port groups inthe H reference signal resource port group.

Solution 2

In Solution 2, channel information sent by a first device 101 to asecond device 102 is shown in the following Table 2.

TABLE 2 Channel information in Solution 2 Channel information MeaningDescription First channel Identification information of N informationantenna ports in M antenna ports for a reference signal Second channelWeighted combination factor Used for performing weighted informationcombination on the N antenna ports, and including a first factor and/ora second factor First factor: amplitude factor Second factor: phasefactor or time delay factor Third channel Phase difference between twoinformation groups of antenna ports obtained by grouping the M antennaports

Optionally, the weighted combination factor indicated by the secondchannel information includes an element 0.

In Solution 2, a manner of constructing a precoding matrix is asfollows.

1. A precoding matrix whose rank is 1 is constituted based on the firstchannel information, the second channel information, and the thirdchannel information in the following manner:

${W = {{\frac{1}{q\; }\begin{bmatrix}e_{m_{0}} & \ldots & e_{m_{N - 1}} & 0 & 0 & 0 \\0 & 0 & 0 & e_{m_{0}} & \ldots & e_{m_{N - 1}}\end{bmatrix}}\begin{bmatrix}c_{k} \\{\phi_{n}c_{k}}\end{bmatrix}}};{where}$ ${c_{k} = \begin{bmatrix}c_{k,0} & \ldots & c_{k,m} & \ldots & c_{k,{N - 1}}\end{bmatrix}^{T}},{and}$ ${B_{i} = \begin{bmatrix}b_{i,0} & \ldots & b_{i,m} & \ldots & b_{i,{M - 1}}\end{bmatrix}};{{and}\begin{bmatrix}e_{m_{0}} & \ldots & e_{m_{N - 1}} & 0 & 0 & 0 \\0 & 0 & 0 & e_{m_{0}} & \ldots & e_{m_{N - 1}}\end{bmatrix}}$

corresponds to the first channel information; c_(k) is a weightedcombination factor used for performing weighted combination on N/2ports, where c_(k,0) is used to perform weighting on an m₀ ^(th) portand an (m₀+N/2)^(th) port, c_(k,m) is used to perform weighting on anm_(m) ^(th) port and an (m_(m)+N/2)^(th) port, and c_(k,N-1) is used toperform weighting on an m_(N-1) ^(th) port and an (m_(N-1)+N/2)^(th)port; m is an integer, and 0≤m≤M−1; φ_(n) is the phase difference thatis between the two groups of antenna ports for the reference signal andthat is indicated by the third channel information; a quantity of rowsof e_(m) ₀ ˜e_(m) _(N-1) is M; and ∥q∥ is a normalization factor.

Optionally, the first device 101 sends, to the second device 102,information used to indicate a value of N, or the first device 101receives, from the second device 102, information used to indicate avalue of N.

Optionally, the first channel information is used to indicate

$\quad{\begin{bmatrix}e_{m_{0}} & \ldots & e_{m_{N - 1}} & 0 & 0 & 0 \\0 & 0 & 0 & e_{m_{0}} & \ldots & e_{m_{N - 1}}\end{bmatrix}.}$

Alternatively, the first channel information includes M bits. In the Mbits, an m₀ ^(th) bit to an m_(N-1) ^(th) bit are 1, and remaining bitsare 0.

2. A precoding matrix whose rank is 2 is constituted based on the firstchannel information, the second channel information, and the thirdchannel information in the following manner:

${W = {\frac{1}{q\; }\begin{bmatrix}{E_{i} \cdot c_{k}} & {E_{j} \cdot c_{y}} \\{\phi_{n}{E_{i} \cdot c_{k}}} & {{- \phi_{n}}{E_{j} \cdot c_{y}}}\end{bmatrix}}};{where}$ ${c_{k} = \begin{bmatrix}c_{k,0} & \ldots & c_{k,m} & \ldots & c_{k,{R - 1}}\end{bmatrix}^{T}},{{E_{i} = \begin{bmatrix}e_{i_{0}} & \ldots & e_{i_{m}} & \ldots & e_{i_{R - 1}}\end{bmatrix}};}$ ${c_{y} = \begin{bmatrix}c_{y,0} & \ldots & c_{y,n} & \ldots & c_{y,{S - 1}}\end{bmatrix}^{T}},{{E_{j} = \begin{bmatrix}e_{j_{0}} & \ldots & e_{j_{n}} & \ldots & e_{j_{S - 1}}\end{bmatrix}};}$

R and S are positive integers, R≤M, and S≤M; and

c_(k) and c_(y) are weighted combination factors, where c_(k,0) is usedto perform weighting on an i₀ ^(th) port and an (i₀+N/2)^(th) port,c_(k,m) is used to perform weighting on an i_(m) ^(th) port and an(i_(m)+N/2)^(th) port, c_(k,R-1) is used to perform weighting on ani_(R-1) ^(th) port and an (i_(R-1)+N/2)^(th) port, c_(y,0) is used toperform weighting on a j₀ ^(th) port and a (j₀+N/2)^(th) port, c_(y,n)is used to perform weighting on a j_(n) ^(th) port and a(j_(n)+N/2)^(th) port, and c_(y,S-1) is used to perform weighting on aj_(S-1) ^(th) port and a (j_(S-1)+N/2)^(th) port; m is an integer, and0≤m≤R−1; n is an integer, and 0≤n≤S−1; φ_(n) is the phase differencethat is between the two groups of antenna ports for the reference signaland that is indicated by the third channel information; and ∥q∥ is anormalization factor.

Optionally, E_(i) is the same as E_(j), and c_(k) is different fromc_(m); or

E_(i) is different from E_(j), and c_(k) is the same as c_(m); or

E_(i) is different from E_(j), and c_(k) is different from c_(m); or

E_(i) is the same as E_(j), and c_(k) is the same as c_(m).

3. The second channel information is a time delay factor, and a formthat is of the precoding matrix including the first channel informationand the second channel information and that is in time domain is asfollows:

${{W(\tau)} = {\sum\limits_{m = 0}^{N - 1}{e_{i_{m}}p_{m}{\delta \left( {\tau - \tau_{m}} \right)}}}};$

where

τ_(m) is the time delay factor corresponding to an m^(th) vector in theN first vectors.

Herein, for example, the reference signal is a channel stateinformation-reference signal (CSI-RS) on which beamforming is performed.Herein, a beam direction has been formed after precoding processing isperformed on each antenna port for the reference signal, and theprecoding may be digital beamforming or analog beamforming.

As shown in FIG. 11, four beam directions b0, b1, b2, and b3respectively correspond to antenna ports: a port 0, a port 1, a port 2,and a port 3.

FIG. 11 shows only beams formed by antennas in one polarizationdirection. If a dual-polarized antenna is considered, two groups ofantennas in two polarization directions each generate a same beamdirection. As shown in FIG. 12, one group of four antennas on a leftside generate a beam 1, a beam 2, a beam 3, and a beam 4 throughprecoding and weighting, and correspondingly, the other group of fourantennas in a polarization direction on a right side generate a beam 1,a beam 2, a beam 3, and a beam 4 through precoding and weighting. Thesecond device 102 sends CSI-RSs on eight antenna ports in total.

It is assumed that there are four propagation paths from the seconddevice 102 to the first device 101: a direct path: a ray 1, andreflection paths: a ray 0, a ray 2, and a ray 3. The second device 102transmits four beams for scanning, which are respectively a beam 0, abeam 1, a beam 2, and a beam 3. Because the beam 0, the beam 2, and thebeam 3 match the propagation paths better, the first device 101 mayreceive energy of b0, b2, and b3. Because a beam in the direction b1 hasno propagation path, the first device 101 cannot detect energy of thebeam.

The first device 101 determines a port 0, a port 2, and a port 3 thatcorrespond to the beams b0, b2, and b3 whose detected energy exceeds aspecific threshold, and determines a port 4, a port 6, and a port 7 inthe other polarization direction. The first device 101 reports antennaport selection information (namely, the first channel information), andreports amplitude and phase weighting information (namely, the secondchannel information) on each antenna port.

W=W_(s)W₂, where

${W_{s} = \begin{bmatrix}e_{m} & e_{n} \\e_{m} & e_{n}\end{bmatrix}},e_{m}$

is a unit vector,

${e_{1} = \begin{bmatrix}1 \\0 \\0 \\0\end{bmatrix}},{e_{2} = \begin{bmatrix}0 \\1 \\0 \\0\end{bmatrix}},e_{m}$

is a column vector in which an m^(th) element is 1 and all otherelements are 0, a dimension of the column vector of e_(m) is equal tohalf of a quantity of ports for the reference signal corresponding toW′₁.

Channel information feedback manner:

Regardless of Solution 1 or Solution 2, when feeding back channelinformation, the first device 101 may use different feedback manners fordifferent channel information.

In the following description, a feedback manner of the first channelinformation, a feedback manner of the second channel information, and afeedback manner of the third channel information are applicable to bothSolution 1 and Solution 2, but content of the channel information isdifferent in Solution 1 and Solution 2. A feedback manner of the fourthchannel information and a feedback manner of the seventh channelinformation are applicable to only Solution 1.

Various feedback manners are specifically described below.

The feedback manner includes wideband based feedback or subband basedfeedback, a feedback period, and analog feedback or feedback afterquantization. The feedback manners are described below one by one.

I. Wideband Based Feedback or Subband Based Feedback

The wideband based feedback means that, for entire system bandwidth,channel information is fed back only once in one feedback period.

The subband based feedback means that, for a plurality of subbandspreset in system bandwidth, channel information is fed back on eachsubband in one feedback period.

When the subband based feedback is used, channel information feedbackprecision is higher, but information overheads are also relativelylarge. When the wideband based feedback is used, channel informationfeedback precision is low, and accordingly information overheads arerelatively small. The subband based feedback may be used for somechannel information that is important to channel feature restoration, orfor channel information in which a difference between values ofdifferent subbands is relatively large. The wideband based feedback maybe used for channel information that is less important to channelfeature restoration, or for channel information in which a differencebetween values of different subbands is small.

Referring to FIG. 9, it is assumed that an entire system frequency bandis divided in advance into ten subbands: a subband 1 to a subband 10.The subband based feedback means that the first device 101 generatescorresponding channel information for each of the ten subbands. Thewideband based feedback means that the first device 101 generates onepiece of channel information for the entire system frequency band.

II. Feedback Period

Some channel information that is important to channel featurerestoration or channel information that changes relatively fast withtime may be fed back by using a relatively short feedback period.Channel information that is less important to channel featurerestoration or channel information that changes relatively slowly withtime may be fed back by using a relatively long feedback period.

III. Analog Feedback or Feedback after Quantization

Some channel information that is important to channel featurerestoration may be fed back after being quantized in a high-precisionquantization manner, for example, by using a relatively largequantization order. Channel information that is less important tochannel feature restoration may be fed back after being quantized in alow-precision quantization manner.

A purpose of using different feedback manners for different channelinformation is to ensure channel information feedback precision, so thata high-precision precoding matrix can be generated, and to reduce aninformation feedback amount as much as possible.

In practice, different feedback manners may be used based on differentproduct implementations.

For example, for wideband based feedback or subband based feedback, anyfeedback manner in Table 3 may be used.

TABLE 3 Feedback manner of wideband based feedback or subband basedfeedback First Second Third Fourth Feedback channel channel channelchannel manner information information information informationDescription Manner 1 Wideband Subband Not fed back Not fed back basedbased feedback feedback Manner 2 Subband Subband Not fed back Not fedback Feedback bandwidth for the based based first channel information isfeedback feedback greater than feedback bandwidth for the second channelinformation Manner 3 Wideband Subband Subband Not fed back based basedbased feedback feedback feedback Manner 4 Subband Subband Subband Notfed back Feedback bandwidth for the based based based first channelinformation is feedback feedback feedback greater than feedbackbandwidth for the second channel information and feedback bandwidth forthe third channel information Manner 5 Wideband Wideband Subband Not fedback based based based feedback feedback feedback Manner 6 SubbandSubband Subband Not fed back Both feedback bandwidth for based basedbased the first channel information feedback feedback feedback andfeedback bandwidth for the second channel information are greater thanfeedback bandwidth for the third channel information Manner 7 WidebandSubband Subband Subband based based based based feedback feedbackfeedback feedback Manner 8 Subband Subband Subband Subband Feedbackbandwidth for the based based based based first channel information isfeedback feedback feedback feedback greater than feedback bandwidth forthe second channel information, feedback bandwidth for the third channelinformation, and feedback bandwidth for the fourth channel informationManner 9 Wideband Wideband Subband Subband Feedback bandwidth for thebased based based based first channel information and feedback feedbackfeedback feedback feedback bandwidth for the second channel informationare greater than feedback bandwidth for the third channel informationand feedback bandwidth for the fourth channel information Manner SubbandSubband Subband Subband 10 based based based based feedback feedbackfeedback feedback Manner Wideband Wideband Subband Wideband 11 basedbased based based feedback feedback feedback feedback Manner SubbandSubband Subband Subband Feedback bandwidth for the 12 based based basedbased first channel information, feedback feedback feedback feedbackfeedback bandwidth for the second channel information, and feedbackbandwidth for the fourth channel information are greater than feedbackbandwidth for the third channel information Manner Wideband SubbandSubband Wideband 13 based based based based feedback feedback feedbackfeedback Manner Subband Subband Subband Subband Feedback bandwidth forthe 14 based based based based first channel information and feedbackfeedback feedback feedback feedback bandwidth for the fourth channelinformation are greater than feedback bandwidth for the second channelinformation and feedback bandwidth for the third channel information

For a feedback period, the following optional manners may be used.

Manner 1

A feedback period of the first channel information is longer than afeedback period of the second channel information, and the third channelinformation and the fourth channel information are not fed back.

Manner 2

A feedback period of the first channel information is longer than afeedback period of the second channel information and a feedback periodof the third channel information, and the fourth channel information isnot fed back.

Manner 3

A feedback manner of the first channel information and a feedback mannerof the second channel information are long-term feedback, and a feedbackmanner of the third channel information is short-term feedback.

Manner 4

Both a feedback period of the first channel information and a feedbackperiod of the second channel information are longer than a feedbackperiod of the third channel information.

Manner 5

A feedback period of the first channel information is longer than afeedback period of the second channel information, a feedback period ofthe third channel information, and a feedback period of the fourthchannel information.

Manner 6

A feedback period of the first channel information and a feedback periodof the second channel information are longer than a feedback period ofthe third channel information and a feedback period of the fourthchannel information.

Manner 7

A feedback period of the first channel information, a feedback period ofthe second channel information, and a feedback period of the fourthchannel information are longer than a feedback period of the thirdchannel information.

Manner 8

A feedback period of the first channel information and a feedback periodof the fourth channel information are longer than a feedback period ofthe second channel information and a feedback period of the thirdchannel information.

In addition to feeding back the foregoing channel information, the firstdevice 101 may measure the reference signal sent by the second device102, to obtain fifth channel information and/or sixth channelinformation, and send the information to the second device 102.

The fifth channel information includes information used to indicate anamount of spatially multiplexed data from the second device 102 to thefirst device 101, for example, an RI in an LTE system. The sixth channelinformation includes information used to indicate channel quality of achannel from the second device 102 to the first device 101, for example,a CQI in the LTE system. A feedback manner of the fifth channelinformation and a feedback manner of the sixth channel information areapplicable to both Solution 1 and Solution 2.

When the third channel information and the fourth channel informationare not fed back, the following channel information feedback manners maybe used.

The first channel information and the fifth channel information are fedback in a first subframe by using a first period, and the second channelinformation and the sixth channel information are fed back in a secondsubframe by using a second period, where the first period is not lessthan the second period; or

the first channel information and the fifth channel information are fedback in a first subframe by using a first period, the second channelinformation is fed back in a second subframe by using a second period,and the sixth channel information is fed back in a third subframe byusing a third period, where the first period is not less than the secondperiod, and the second period is not less than the third period; or

the first channel information and the fifth channel information are fedback in a first subframe by using a first period, the second channelinformation is fed back in a second subframe by using a second period,and the sixth channel information is fed back in a third subframe byusing a third period, where the first period is not less than the secondperiod, and the second period is not less than the third period; or

the fifth channel information is fed back in a first subframe by using afirst period, the first channel information is fed back in a secondsubframe by using a second period, the second channel information is fedback in a third subframe by using a third period, and the sixth channelinformation is fed back in a fourth subframe by using a fourth period,where the first period is not less than the second period, the secondperiod is not less than the third period, and the third period is notless than the fourth period.

When the fourth channel information is not fed back, the followingchannel information feedback manners may be used.

The first channel information and the fifth channel information are fedback in a first subframe by using a first period, the second channelinformation and the third channel information are fed back in a secondsubframe by using a second period, and the sixth channel information isfed back in a third subframe by using a third period, where the firstperiod is not less than the second period, and the second period is notless than the third period; or

the first channel information and the fifth channel information are fedback in a first subframe by using a first period, and the second channelinformation, the third channel information, and the sixth channelinformation are fed back in a second subframe by using a second period,where the first period is not less than the second period; or

the first channel information, the second channel information, and thefifth channel information are fed back in a first subframe by using afirst period, and the third channel information and the sixth channelinformation are fed back in a second subframe by using a second period,where the first period is not less than the second period; or

the first channel information and the fifth channel information are fedback in a first subframe by using a first period, the second channelinformation is fed back in a second subframe by using a second period,and the third channel information and the sixth channel information arefed back in a third subframe by using a third period, where the firstperiod is not less than the second period, and the second period is notless than the third period; or

the first channel information and the fifth channel information are fedback in a first subframe by using a first period, the second channelinformation is fed back in a second subframe by using a second period,the third channel information is fed back in a third subframe by using athird period, and the sixth channel information is fed back in a fourthsubframe by using a fourth period, where the first period is not lessthan the second period, the second period is not less than the thirdperiod, and the third period is not less than the fourth period; or

the fifth channel information is fed back in a first subframe by using afirst period, the first channel information is fed back in a secondsubframe by using a second period, the second channel information is fedback in a third subframe by using a third period, the third channelinformation is fed back in a fourth subframe by using a fourth period,and the sixth channel information is fed back in a fifth subframe byusing a fifth period, where the first period is not less than the secondperiod, the second period is not less than the third period, the thirdperiod is not less than the fourth period, and the fourth period is notless than the fifth period.

When both the third channel information and the fourth channelinformation are fed back, the following channel information feedbackmanners may be used.

The first channel information, the fourth channel information, and thefifth channel information are fed back in a first subframe by using afirst period, the second channel information and the third channelinformation are fed back in a second subframe by using a second period,and the sixth channel information is fed back in a third subframe byusing a third period, where the first period is not less than the secondperiod, and the second period is not less than the third period; or

the first channel information, the fourth channel information, and thefifth channel information are fed back in a first subframe by using afirst period, and the second channel information, the third channelinformation, and the sixth channel information are fed back in a secondsubframe by using a second period, where the first period is not lessthan the second period; or

the fifth channel information is fed back in a first subframe by using afirst period, the first channel information and the fourth channelinformation are fed back in a second subframe by using a second period,the second channel information and the third channel information are fedback in a third subframe by using a third period, and the sixth channelinformation is fed back in a fourth subframe by using a fourth period,where the first period is not less than the second period, the secondperiod is not less than the third period, and the third period is notless than the fourth period; or

the fifth channel information is fed back in a first subframe by using afirst period, the first channel information and the fourth channelinformation are fed back in a second subframe by using a second period,and the second channel information, the third channel information, andthe sixth channel information are fed back in a third subframe by usinga third period, where the first period is not less than the secondperiod, and the second period is not less than the third period; or

the fifth channel information, the first channel information, the secondchannel information, and the fourth channel information are fed back ina first subframe by using a first period, and the third channelinformation and the sixth channel information are fed back in a secondsubframe by using a second period, where the first period is not lessthan the second period; or

the fifth channel information, the first channel information, and thefourth channel information are fed back in a first subframe by using afirst period, the second channel information is fed back in a secondsubframe by using a second period, and the third channel information andthe sixth channel information are fed back in a third subframe by usinga third period, where the first period is not less than the secondperiod, and the second period is not less than the third period; or

the fifth channel information, the first channel information, and thefourth channel information are fed back in a first subframe by using afirst period, the second channel information is fed back in a secondsubframe by using a second period, the third channel information is fedback in a third subframe by using a third period, and the sixth channelinformation is fed back in a fourth subframe by using a fourth period,where the first period is not less than the second period, the secondperiod is not less than the third period, and the third period is notless than the fourth period; or

the fifth channel information is fed back in a first subframe by using afirst period, the first channel information and the fourth channelinformation are fed back in a second subframe by using a second period,the second channel information is fed back in a third subframe by usinga third period, the third channel information is fed back in a fourthsubframe by using a fourth period, and the sixth channel information isfed back in a fifth subframe by using a fifth period, where the firstperiod is not less than the second period, the second period is not lessthan the third period, the third period is not less than the fourthperiod, and the fourth period is not less than the fifth period.

FIG. 10A and FIG. 10B show a possible channel information feedbackmanner.

For analog feedback or quantization feedback, a flexible feedback mannermay be used for the second channel information.

For example, the second channel information includes third subchannelinformation, and the third subchannel information is used to indicatethe first factor. The third subchannel information is not quantized.Alternatively, first quantization is performed on the third subchannelinformation, and a quantization order of the first quantization is notgreater than a preset first-quantization order threshold.

Optionally, the second channel information includes fourth subchannelinformation, and the fourth subchannel information is used to indicatethe second factor. The fourth subchannel information is not quantized.Alternatively, second quantization is performed on the fourth subchannelinformation, and a quantization order of the second quantization is notgreater than a preset second-quantization order threshold.

FIG. 13 is a schematic structural diagram of a first device according toan embodiment of the present invention. As shown in FIG. 13, the firstdevice includes a receiving module 1301, a processing module 1302, and asending module 1303.

In an optional implementation,

the receiving module 1301 is configured to receive a reference signalsent by a second device, where the reference signal is sent on S antennaports, the S antenna ports belong to H reference signal resource portgroups, and S and H are integers greater than or equal to 1;

the processing module 1302 is configured to measure the reference signalto obtain first channel information and second channel information; and

the sending module 1303 is configured to send the first channelinformation and the second channel information to the second device.

The first channel information includes identification information of Mfirst vectors, where M is an integer not less than 2.

The second channel information includes information about a weightedcombination factor used for performing weighted combination on N firstvectors in the M first vectors, where N is a positive integer notgreater than M.

The weighted combination factor includes a first factor and/or a secondfactor.

The first factor is an amplitude factor, and the second factor is aphase factor or a time delay factor.

The first channel information and the second channel information areused to constitute a precoding matrix.

A dimension of the first vector is a quantity of antenna ports in eachreference signal resource port group, or a dimension of the first vectoris half of a quantity of antenna ports in each reference signal resourceport group.

In this optional implementation, for another optional implementation ofthe first device, refer to the first device 101 in Solution 1. Thereceiving module 1301 is configured to perform a receiving operation ofthe first device 101, the processing module 1302 is configured toperform a processing operation of the first device 101, and the sendingmodule 1303 is configured to perform a sending operation of the firstdevice 101.

In another optional implementation,

the receiving module 1301 is configured to receive a reference signalsent by a second device;

the processing module 1302 is configured to measure the reference signalto obtain first channel information and second channel information; and

the sending module 1303 is configured to send the first channelinformation and the second channel information to the second device.

The first channel information includes identification information of Nantenna ports in M antenna ports for the reference signal, where M is aninteger not less than 2, and N is a positive integer not greater than M.

The second channel information includes information about a weightedcombination factor used for performing weighted combination on the Nantenna ports.

The weighted combination factor includes a first factor and/or a secondfactor.

The first factor is an amplitude factor, and the second factor is aphase factor or a time delay factor.

The first channel information and the second channel information areused to constitute a precoding matrix.

In this optional implementation, for another optional implementation ofthe first device, refer to the first device 101 in Solution 2. Thereceiving module 1301 is configured to perform a receiving operation ofthe first device 101, the processing module 1302 is configured toperform a processing operation of the first device 101, and the sendingmodule 1303 is configured to perform a sending operation of the firstdevice 101.

Optionally, the receiving module 1301 may be implemented by a receiver,the processing module 1302 may be implemented by a processor, and thesending module 1303 may be implemented by a transmitter.

FIG. 14 is a schematic structural diagram of a second device accordingto an embodiment of the present invention. As shown in FIG. 14, thesecond device includes a receiving module 1401, a processing module1402, and a sending module 1403.

In an optional implementation,

the sending module 1403 is configured to send a reference signal to afirst device, where the reference signal is sent on S antenna ports, theS antenna ports belong to H reference signal resource port groups, and Sand H are integers greater than or equal to 1;

the receiving module 1401 is configured to receive first channelinformation and second channel information from the first device, wherethe first channel information and the second channel information areobtained by the first device by measuring the received reference signal,where

the first channel information includes identification information of Mfirst vectors, where M is an integer not less than 2;

the second channel information includes information about a weightedcombination factor used for performing weighted combination on N firstvectors in the M first vectors, where N is a positive integer notgreater than M;

the weighted combination factor includes a first factor and/or a secondfactor;

the first factor is an amplitude factor, and the second factor is aphase factor or a time delay factor; and

a dimension of the first vector is a quantity of antenna ports in eachreference signal resource port group, or a dimension of the first vectoris half of a quantity of antenna ports in each reference signal resourceport group; and

the processing module 1402 is configured to generate the precodingmatrix based on the first channel information and the second channelinformation.

The sending module 1403 is further configured to send data to the firstdevice based on the precoding matrix generated by the processing module.

In this optional implementation, for another optional implementation ofthe second device, refer to the second device 102 in Solution 1. Thereceiving module 1401 is configured to perform a receiving operation ofthe second device 102, the processing module 1402 is configured toperform a processing operation of the second device 102, and the sendingmodule 1403 is configured to perform a sending operation of the seconddevice 102.

In another optional implementation,

the sending module 1403 is configured to send a reference signal to afirst device;

the receiving module 1401 is configured to receive first channelinformation and second channel information from the first device, wherethe first channel information and the second channel information areobtained by the first device by measuring the received reference signal,where

the first channel information includes identification information of Nantenna ports in M antenna ports for the reference signal, where M is aninteger not less than 2, and N is a positive integer not greater than M;

the second channel information includes information about a weightedcombination factor used for performing weighted combination on the Nantenna ports;

the weighted combination factor includes a first factor and/or a secondfactor; and

the first factor is an amplitude factor, and the second factor is aphase factor or a time delay factor; and

the processing module 1402 is configured to generate a precoding matrixbased on the first channel information and the second channelinformation.

The sending module 1403 is further configured to send data to the firstdevice based on the precoding matrix generated by the processing module1402.

In this optional implementation, for another optional implementation ofthe second device, refer to the second device 102 in Solution 2. Thereceiving module 1401 is configured to perform a receiving operation ofthe second device 102, the processing module 1402 is configured toperform a processing operation of the second device 102, and the sendingmodule 1403 is configured to perform a sending operation of the seconddevice 102.

Persons skilled in the art should understand that the embodiments of thepresent invention may be provided as a method, a system, or a computerprogram product. Therefore, the present invention may use a form ofhardware only embodiments, software only embodiments, or embodimentswith a combination of software and hardware. Moreover, the presentinvention may use a form of a computer program product that isimplemented on one or more computer-usable storage media (including butnot limited to a disk memory, a CD-ROM, an optical memory, and the like)that include computer-usable program code.

The present invention is described with reference to the flowchartsand/or block diagrams of the method, the device (system), and thecomputer program product according to the embodiments of the presentinvention. It should be understood that computer program instructionsmay be used to implement each process and/or each block in theflowcharts and/or the block diagrams and a combination of a processand/or a block in the flowcharts and/or the block diagrams. Thesecomputer program instructions may be provided for a general-purposecomputer, a dedicated computer, an embedded processor, or a processor ofany other programmable data processing device to generate a machine, sothat the instructions executed by a computer or a processor of any otherprogrammable data processing device generate an apparatus forimplementing a specific function in one or more processes in theflowcharts and/or in one or more blocks in the block diagrams.

These computer program instructions may alternatively be stored in acomputer readable memory that can instruct the computer or any otherprogrammable data processing device to work in a specific manner, sothat the instructions stored in the computer readable memory generate anartifact that includes an instruction apparatus. The instructionapparatus implements a specific function in one or more processes in theflowcharts and/or in one or more blocks in the block diagrams.

These computer program instructions may alternatively be loaded onto acomputer or another programmable data processing device, so that aseries of operations and steps are performed on the computer or theanother programmable device, thereby generating computer-implementedprocessing. Therefore, the instructions executed on the computer or theanother programmable device provide steps for implementing a specificfunction in one or more processes in the flowcharts and/or in one ormore blocks in the block diagrams.

Although embodiments of the present invention have been described,persons skilled in the art can make changes and modifications to theseembodiments once they learn the basic inventive concept. Therefore, thefollowing claims are intended to be construed as to cover theembodiments and all changes and modifications falling within the scopeof the present invention.

Obviously, persons skilled in the art can make various modifications andvariations to the embodiments of the present invention without departingfrom the spirit and scope of the embodiments of the present invention.The present invention is intended to cover these modifications andvariations provided that they fall within the scope of protectiondefined by the following claims and their equivalent technologies.

What is claimed is:
 1. A first device, comprising: a processor; areceiver that receives a reference signal; and a memory, configured tostore at least one computer instruction which, when executed by theprocessor, cause the processor to measure the reference signal from thereceiver to obtain first channel information and second channelinformation and send the first channel information and the secondchannel information to the second device, wherein the first channelinformation comprises identification information of N antenna ports in Mantenna ports for the reference signal, M is an integer not less than 2,and N is a positive integer not greater than M; the second channelinformation comprises information about a weighted combination factorused for performing weighted combination on the N antenna ports, theweighted combination factor comprises an amplitude factor and a phasefactor; and the first channel information and the second channelinformation are used to constitute a precoding matrix.
 2. The firstdevice according to claim 1, further comprising: a sending module thatreceives information from the processor, wherein the processor isfurther measures the reference signal to obtain third channelinformation and the sending module sends the third channel informationto the second device, the third channel information comprises a phasedifference between two groups of antenna ports obtained by grouping theM antenna ports; and the third channel information is also used toconstitute the precoding matrix.
 3. The first device according to claim1, wherein the weighted combination factor is a product of the amplitudeand phase factor.
 4. The first device according to claim 3, wherein theamplitude factor is selected from a first amplitude factor set and thephase factor is selected from a first phase factor set.
 5. The firstdevice according to claim 1, wherein a feedback manner of the firstchannel information is bandwidth based feedback, and a feedback mannerof the second channel information is subband based feedback.
 6. Adevice, comprising: a processor; a transmitter that sends a referencesignal; a receiver that receives a first and second channel information;and a memory, configured to store at least one computer instructionswhich, when executed by the processor, cause the processor sending thereference signal, receive through the receiver the first and secondchannel information, wherein the first and second channel informationare obtained by the first device by measuring the received referencesignal, the first channel information comprises identificationinformation of N antenna ports in M antenna ports for the referencesignal, wherein M is an integer not less than 2, and N is a positiveinteger not greater than M, the second channel information comprisesinformation about a weighted combination factor used for performingweighted combination on the N antenna ports, the weighted combinationfactor comprises an amplitude factor and a phase factor, generating aprecoding matrix based on the first channel information and the secondchannel information, and sending data to the first device based on theprecoding matrix generated by the processing module.
 7. The deviceaccording to claim 6, wherein the processor is further configured toreceive third channel information from the first device, wherein thethird channel information is obtained by the first device by measuringthe reference signal, the third channel information comprises a phasedifference between two groups of antenna ports obtained by grouping theM antenna ports and the processing module is specifically configured togenerate the precoding matrix based on the first channel information,the second channel information, and the third channel information. 8.The device according to claim 6, wherein the weighted combination factoris a product of the first factor and the second factor.
 9. The deviceaccording to claim 8, wherein the first factor is selected from a firstfactor set and the second factor is selected from a second factor set.10. The device according to claim 6, wherein a feedback manner of thefirst channel information is bandwidth based feedback, and a feedbackmanner of the second channel information is subband based feedback. 11.A channel information sending method, comprising: receiving, by a firstdevice, a reference signal sent by a second device; measuring, by thefirst device, the received reference signal to obtain first channelinformation and second channel information; and sending, by the firstdevice, the first channel information and the second channel informationto the second device, wherein the first channel information comprisesidentification information of N antenna ports in M antenna ports for thereference signal, wherein M is an integer not less than 2, and N is apositive integer not greater than M, the second channel informationcomprises information about a weighted combination factor used forperforming weighted combination on the N antenna ports, the weightedcombination factor comprises a first factor and a second factor, thefirst factor is an amplitude factor, and the second factor is a phasefactor or a time delay factor, and the first channel information and thesecond channel information are used to constitute a precoding matrix.12. The method according to claim 11, further comprising: measuring, bythe first device, the reference signal to obtain third channelinformation; and sending, by the first device, the third channelinformation to the second device, wherein the third channel informationcomprises a phase difference between two groups of antenna portsobtained by grouping the M antenna ports and the third channelinformation is also used to constitute the precoding matrix.
 13. Themethod according to claim 11, wherein the weighted combination factor isa product of the first factor and the second factor.
 14. The methodaccording to claim 13, wherein the first factor is selected from a firstfactor set and the second factor is selected from a second factor set.15. The method according to claim 11, wherein a feedback manner of thefirst channel information is bandwidth based feedback, and a feedbackmanner of the second channel information is subband based feedback. 16.A data sending method, comprising: sending, by a second device, areference signal to a first device; receiving, by the second device,first channel information and second channel information from the firstdevice, wherein the first channel information and the second channelinformation are obtained by the first device by measuring the receivedreference signal, wherein the first channel information comprisesidentification information of N antenna ports in M antenna ports for thereference signal, wherein M is an integer not less than 2, and N is apositive integer not greater than M; the second channel informationcomprises information about a weighted combination factor used forperforming weighted combination on the N antenna ports, the weightedcombination factor comprises a first factor and a second factor, and thefirst factor is an amplitude factor, and the second factor is a phasefactor or a time delay factor; generating, by the second device, aprecoding matrix based on the first channel information and the secondchannel information; and sending, by the second device, data to thefirst device based on the generated precoding matrix.
 17. The methodaccording to claim 16, further comprising: receiving, by the seconddevice, third channel information from the first device, wherein thethird channel information is obtained by the first device by measuringthe reference signal, wherein the third channel information comprises aphase difference between two groups of antenna ports obtained bygrouping the M antenna ports and the generating, by the second device,the precoding matrix based on the first channel information and thesecond channel information comprises: generating, by the second device,the precoding matrix based on the first channel information, the secondchannel information, and the third channel information.
 18. The methodaccording to claim 16, wherein the weighted combination factor is aproduct of the first factor and the second factor.
 19. The methodaccording to claim 18, wherein the first factor is selected from a firstfactor set and the second factor is selected from a second factor set.20. The method according to claim 16, wherein a feedback manner of thefirst channel information is bandwidth based feedback, and a feedbackmanner of the second channel information is subband based feedback. 21.A non-transitory computer readable storage medium method, configured tostore a computer program instruction which, when executed by aprocessor, cause the processor to perform operations comprising:receiving, a reference signal; measuring, the received reference signalto obtain first channel information and second channel information; andsending, the first channel information and the second channelinformation, wherein the first channel information comprisesidentification information of N antenna ports in M antenna ports for thereference signal, wherein M is an integer not less than 2, and N is apositive integer not greater than M, the second channel informationcomprises information about a weighted combination factor used forperforming weighted combination on the N antenna ports, the weightedcombination factor comprises a first factor and a second factor, thefirst factor is an amplitude factor, and the second factor is a phasefactor or a time delay factor, and the first channel information and thesecond channel information are used to constitute a precoding matrix.22. A non-transitory computer readable storage medium method, configuredto store a computer program instruction which, when executed by aprocessor, cause the processor to perform operations comprising:sending, a reference signal; receiving, first channel information andsecond channel information, wherein the first channel information andthe second channel information are obtained by measuring the receivedreference signal, wherein the first channel information comprisesidentification information of N antenna ports in M antenna ports for thereference signal, wherein M is an integer not less than 2, and N is apositive integer not greater than M, the second channel informationcomprises information about a weighted combination factor used forperforming weighted combination on the N antenna ports, the weightedcombination factor comprises a first factor and a second factor, and thefirst factor is an amplitude factor, and the second factor is a phasefactor or a time delay factor; generating, a precoding matrix based onthe first channel information and the second channel information; andsending, data based on the generated precoding matrix.